US5536807A - Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof - Google Patents

Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof Download PDF

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US5536807A
US5536807A US08/110,394 US11039493A US5536807A US 5536807 A US5536807 A US 5536807A US 11039493 A US11039493 A US 11039493A US 5536807 A US5536807 A US 5536807A
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lactide
film
polymer
poly
percent
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Patrick R. Gruber
Jeffrey J. Kolstad
Christopher M. Ryan
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Cargill Inc
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Cargill Inc
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Application filed by Cargill Inc filed Critical Cargill Inc
Priority to US08/110,394 priority Critical patent/US5536807A/en
Priority to BR9305660A priority patent/BR9305660A/en
Priority to AU52953/93A priority patent/AU5295393A/en
Priority to AT93923183T priority patent/ATE190337T1/en
Priority to NZ256972A priority patent/NZ256972A/en
Priority to ES93923183T priority patent/ES2142880T3/en
Priority to KR1019940701867A priority patent/KR100326642B1/en
Priority to JP50932194A priority patent/JP3436368B2/en
Priority to CA002124847A priority patent/CA2124847C/en
Priority to DE69328018T priority patent/DE69328018T2/en
Priority to EP93923183A priority patent/EP0615529B1/en
Priority to PCT/US1993/009331 priority patent/WO1994007941A1/en
Assigned to CARGILL, INCORPORATED reassignment CARGILL, INCORPORATED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: GRUBER, PATRICK R., KOLSTAD, JEFFREY J., RYAN, CHRISTOPHER M.
Priority to FI942559A priority patent/FI942559A/en
Priority to NO942038A priority patent/NO942038L/en
Assigned to CARGILL INCORPORATED reassignment CARGILL INCORPORATED ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CONN, ROBIN S. EICHEN, GRUBER, PATRICK R., HALL, ERIC S., RYAN, CHRISTOPHER M., KOLSTAD, JEFFREY J.
Priority to US08/607,090 priority patent/US5773562A/en
Publication of US5536807A publication Critical patent/US5536807A/en
Application granted granted Critical
Priority to US09/036,799 priority patent/US6093791A/en
Priority to US09/361,375 priority patent/US6121410A/en
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    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18Manufacture of films or sheets
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L15/00Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
    • A61L15/16Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
    • A61L15/22Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
    • A61L15/26Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61LMETHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L31/00Materials for other surgical articles, e.g. stents, stent-grafts, shunts, surgical drapes, guide wires, materials for adhesion prevention, occluding devices, surgical gloves, tissue fixation devices
    • A61L31/04Macromolecular materials
    • A61L31/06Macromolecular materials obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/02Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
    • C08G63/06Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
    • C08G63/08Lactones or lactides
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/88Post-polymerisation treatment
    • C08G63/90Purification; Drying
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L67/00Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
    • C08L67/04Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09DCOATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D167/00Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
    • C09D167/04Polyesters derived from hydroxycarboxylic acids, e.g. lactones
    • DTEXTILES; PAPER
    • D01NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01FCHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/58Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
    • D01F6/62Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
    • D01F6/625Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters derived from hydroxy-carboxylic acids, e.g. lactones
    • DTEXTILES; PAPER
    • D04BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04HMAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/40Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties
    • D04H1/42Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres from fleeces or layers composed of fibres without existing or potential cohesive properties characterised by the use of certain kinds of fibres insofar as this use has no preponderant influence on the consolidation of the fleece
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/10Coatings without pigments
    • D21H19/14Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/24Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H19/28Polyesters
    • DTEXTILES; PAPER
    • D21PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21HPULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00Coated paper; Coating material
    • D21H19/36Coatings with pigments
    • D21H19/44Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/62Macromolecular organic compounds or oligomers thereof obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2230/00Compositions for preparing biodegradable polymers
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04Polyesters derived from hydroxy carboxylic acids, e.g. lactones
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08LCOMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L101/00Compositions of unspecified macromolecular compounds
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • Y10T428/31786Of polyester [e.g., alkyd, etc.]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • Y10T428/31786Of polyester [e.g., alkyd, etc.]
    • Y10T428/3179Next to cellulosic
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/31504Composite [nonstructural laminate]
    • Y10T428/31801Of wax or waxy material
    • Y10T428/31804Next to cellulosic
    • Y10T428/31808Cellulosic is paper
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
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    • Y10T428/31815Of bituminous or tarry residue
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
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    • Y10T428/31971Of carbohydrate
    • Y10T428/31993Of paper

Definitions

  • the present invention relates to a semi-crystalline film comprising a melt-stable, biodegradable, lactide polymer composition and a process for manufacturing the film from a melt-stable, biodegradable polymer.
  • a sheet In a cast film process, a sheet is typically extruded from a slit die. The sheet is thereafter pulled through a series of rollers which cool the extruded sheet and may also elongate the length and width of the sheet to a desired dimension and thickness.
  • films are widespread and well known in the art.
  • the heaviest use of films occurs in the packaging and disposable article industries.
  • Films employed in the packaging industry include films used in food and non-food packaging, merchandise bags and trash bags.
  • the disposable article industry the general uses of films occur in the construction of diapers and personal hygiene articles, including tapes.
  • films comprising polymers such as polyethylene, polypropylene, polyethylene terephthlate, nylon, polystyrene, polyvinyl chloride and polyvinylidene chloride are popular for their superior extrusion and film-making properties.
  • these films are not biodegradable.
  • these films are generally noncompostable, which is undesirable from an environmental point of view.
  • Films have been developed which are generally considered to be biodegradable. These are films which purportedly have adequate properties to permit them to break down when exposed to conditions which lead to composting. Examples of such arguably biodegradable films include those made from polycaprolactone, starch biopolymers and polyvinyl alcohol.
  • films extruded from these materials have been employed in film containing articles, many problems have been encountered with their use. Often the films are not completely biodegradable or compostable. Furthermore, some biodegradable films may also be unduly sensitive to water, either limiting the use of the film or requiring some type of surface treatment to the film, often rendering the film nonbiodegradable. Others have inadequate heat resistance for wide spread use. Thus, there is a need for a film which is completely biodegradable.
  • the present invention recognizes the importance of crystallinity and further introduces methods to achieve such crystallinity.
  • manufacturers of polymers utilizing processes such as those disclosed by Gruber et al. will convert raw material monomers into polymer beads, resins or other pelletized or powdered products.
  • the polymer in this form may then be sold to end users who convert, i.e., extrude, blow-mold, cast films, blow films, thermoform, injection-mold or fiber-spin the polymer at elevated temperatures to form useful articles.
  • the above processes are collectively referred to as melt-processing.
  • Polymers produced by processes such as those disclosed by Gruber et al., which are to be sold commercially as beads, resins, powders or other non-finished solid forms are generally referred to collectively as polymer resins.
  • lactide polymers or poly(lactide) are unstable.
  • the concept of instability has both negative and positive aspects.
  • a positive aspect is the biodegradation or other forms of degradation which occur when lactide polymers or articles manufactured from lactide polymers are discarded or composted after completing their useful life.
  • a negative aspect of such instability is the degradation of lactide polymers during processing at elevated temperatures as, for example, during melt-processing by end-user purchasers of polymer resins.
  • Lactide polymer degradation at elevated temperature has been the subject of several studies, including: I. C. McNeill and H. A. Leiper, Polymer Degradation and Stability, vol. 11, pp. 267-285 (1985); I. C. McNeill and H. A. Leiper, Polymer Degradation and Stability, vol. 11, pp. 309-326 (1985); M. C. Gupta and V. G. Deshmukh, Colloid & Polymer Science, vol. 260, pp. 308-311 (1982); M. C. Gupta and V. G. Deshmukh, Colloid & Polymer Science, vol. 260, pp. 514-517 (1982); Ingo Luderwald, Dev.
  • One of the proposed reaction pathways includes the reaction of a hydroxyl end group in a "back-biting" reaction to form lactide. This equilibrium reaction is illustrated above.
  • Other proposed reaction pathways include: reaction of the hydroxyl end group in a "back-biting” reaction to form cyclic oligomers, chain scission through hydrolysis of the ester bonds, an intramolecular beta-elimination reaction producing a new acid end group and an unsaturated carbon-carbon bond, and radical chain decomposition reactions.
  • poly(lactide)s have been produced in the past, but primarily for use in medical devices. These polymers exhibit biodegradability, but also a more stringent requirement of being bioresorbable or biocompatible.
  • M. Vert, Die Ingwandte Makromolekulare Chemie, vol. 166-167, pp. 155-168 (1989) "The use of additives is precluded because they can leach out easily in body fluids and then be recognized as toxic, or, at least, they can be the source of fast aging with loss of the properties which motivated their use. Therefore, it is much more suitable to achieve property adjustment through chemical or physical structure factors, even if aging is still a problem.”
  • work aimed at the bioresorbable or biocompatible market focused on poly(lactide) and blends which did not include any additives.
  • poly(lactide) or lactide polymers and copolymers can be given the required physical properties by generating lactide of very high purity by means of such methods as solvent extraction or recrystallization followed by polymerization.
  • the polymer generated from this high purity lactide is a very high molecular weight product which will retain its physical properties even if substantial degradation occurs and the molecular weight drops significantly during processing.
  • the polymer may be precipitated from a solvent in order to remove residual monomer and catalysts.
  • Each of these treatments add stability to the polymer, but clearly at a high cost which would not be feasible for lactide polymer compositions which are to be used to replace inexpensive petrochemical-based polymers in the manufacture of films.
  • the needed melt-stable polymer composition must also exhibit sufficient compostability or degradability after its useful life as a film.
  • the melt-stable polymer must be processable in existing melt-processing equipment, by exhibiting sufficiently low viscosities at melt-processing temperatures while polymer degradation and lactide formation remains below a point of substantial degradation and does not cause excessive fouling of processing equipment.
  • the lactide polymer must retain its molecular weight, viscosity and other physical properties within commercially-acceptable levels through the film manufacturing process.
  • the present invention also offers further advantages over the prior art and solves other problems associated therewith.
  • a semi-crystalline poly(lactide) film exhibiting a net melting endotherm greater than about 10 joules per gram.
  • the semi-crystalline poly(lactide) film comprises a melt-stable, lactide polymer composition comprising: a plurality of poly(lactide) polymer chains, the polymer being a reaction product of polymerizing a lactide mixture comprising less than about 15 percent by weight meso-lactide.
  • the remaining lactide can be L-lactide, D-lactide or mixtures thereof provided that the overall lactide mixture comprises at least about 85% of either the L or D lactide isomer. This area is shown in FIG. 4.
  • the polymer has residual lactide in a concentration of less than about 2 percent by weight; and water in a concentration of less than about 2,000 parts per million.
  • a process for the manufacture of the film is also provided.
  • the film may be manufactured from any number of methods and is not to be limited by the particular method.
  • stabilizing agents in the form of anti-oxidants and water scavengers may be added.
  • plasticizers, nucleating agents, anti-static agents, slip aids and anti-blocking agents may be added.
  • the resultant film is biodegradable and may be disposed of in an environmentally sound fashion.
  • Poly(lactide) is a polymeric material which offers unique advantages as a film not only in the biodegradable sense, but in the manufacturing process as well.
  • the present invention describes a method of increasing the degree of crystallinity in a film or sheet by drawing the film in a machine and/or transverse direction orientation at temperatures near the Tg.
  • the Tg can be lowered to near room temperature through the use of plasticizers.
  • Strain hardening is a phenomenon which, if present, can be used to obtain high quality, uniform, semi-crystalline films.
  • a description of strain hardening in stretching of films of poly(ethylene 2,6, naphthalene dicarboxilate) is given by Cakmak et al. [M. Cakmak, Y. D. Wang, and M. Simhambhatla, Polymer Engineering and Science, June 1990, Vol. 30, p 721-733].
  • Strain hardening can be identified by an increase in the force required to continue elongation of a film. The essential feature of this phenomenon is the appearance of necks (thin areas) during the stretching operation. High amounts of stretching occurs locally in the necked region, causing it to elongate more than the surrounding areas.
  • the films of the present invention may be used in articles such as diapers, packaging film, agricultural mulch film, bags and tape.
  • the films of the present invention are superior in diaper constructions as compared to other films such as polypropylene or polyethylene.
  • the typical construction of a diaper comprises an outer, water impervious back sheet, a middle absorbent layer and an inner layer.
  • the outer back sheet, comprising the exterior of the diaper, is desirable from an environmental point of view if it is biodegradable.
  • the film of the present invention satisfies this environmental concern by being biodegradable and compostable.
  • a poly(lactide) film unlike other biodegradable polymers, is believed to not support microbial growth during storage and typical film use. Starch or other biodegradable polymers, when exposed to warm, damp environments, will promote the growth of unhealthy microbes. This is undesirable in most personal hygiene products. Thus, the present invention has yet another advantage over prior biodegradable polymers.
  • Another advantage of the present invention is the high surface energy of poly(lactide) films.
  • Poly(lactide) is a material with a relatively high surface energy, when compared to other films.
  • a high surface energy film also has the advantage of having a surface which is easier to print on. This is an important feature in packaging applications and diapers.
  • the film of the present invention exhibits a higher surface energy than untreated polyolefin films. In order to produce a satisfactory printing surface, these films must first be modified. This not only increases the costs associated with production of the films, but the modification treatment will diffuse into the film and will produce an unsatisfactory printing surface.
  • the surface energy of substantially pure poly(lactide) films of the present invention is about 44 dynes/cm. This leads to a surface with satisfactory printing characteristics without surface modification. Slip aids or other additives may reduce the surface energy. Additionally, inks which are typically more difficult to apply onto films, like water based inks, may be applied directly to poly(lactide).
  • Poly(lactide) is a relatively low viscosity polymer which allows the extrusion of the film to be done at lower temperatures than traditional films. This results in a cost savings to the converter because the extrusion equipment will not require as much power when run at lower temperatures.
  • Heat sealability is also a property of films which is desirable.
  • Poly(lactide) can be heat sealed at temperatures lower than 70° C., at line pressures lower than 40 psi, and at times less than 2 sec.
  • poly(lactide) it may be advantageous to blend a second polymer with poly(lactide).
  • the polymer chosen for blending with poly(lactide) will be one which has the properties necessary for the particular need and is compatible with poly(lactide) to the extent that the particular properties of poly(lactide) are improved. Incompatibility often results in a polymer blend which has inferior properties, such as very low tensile strength and modulus. Properties which may be increased include elongation, heat resistance, rheological properties, degradability, impact resistance, tear resistance and barrier properties to oxygen, moisture, or carbon dioxide.
  • poly(lactide) it may be advantageous to blend a second polymer with poly(lactide).
  • the polymer chosen for blending with poly(lactide) will be one which has the properties necessary for the particular need. Incompatibility often results in a polymer blend which has inferior properties, such as very low tensile strength, rheological properties, degradability, and barrier properties to oxygen, moisture or carbon dioxide.
  • Polymers which may be useful for improving the film properties of poly(lactide) include aliphatic polyesters or polyamides made by both ring opening and condensation polymerization, esterified cellulose resins, derivitized starch, polyvinylacetate and any of its partially hydrolyzed products including polyvinylalcohol, polyethers including poly(ethylene oxide), polycarbonates, polyurethanes including those based on aliphatic isocyanates, polyanhydrides, natural rubber and its derivatives including epoxidized natural rubber, block copolymers of styrene and isoprene or butadiene and the hydrogenated version of those polymers, polyacrylates and methacrylates, polyolefins, and polystyrene.
  • polymers which are also degradable including poly(caprolactone), poly(hydroxybutyrate hydroxyvalerate), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and poly(vinyl alcohol).
  • poly(lactide) may be blended with poly(lactide) in percentages of 1 to 95% by weight to make films of improved properties as shown in Example 1.
  • FIG. 1 is a schematic representation of a preferred rocks process for the manufacture of a melt-stable lactide polymer composition
  • FIG. 2 is a graph showing the equilibrium relationship between lactide and poly(lactide) at various temperatures.
  • FIG. 3 is a graph showing the melting endotherm for annealed samples of poly(lactide).
  • FIG. 4 is a phase diagram for meso-lactide, L-lactide and D-lactide.
  • lactide polymer compositions used in films disclosed herein focus on meeting the requirements of the melt-processor of a lactide polymer resin such as that produced from a process disclosed by Gruber et al.
  • the present invention is directed to a poly(lactide) film and is not limited to the lactide polymer composition or process of Gruber et al. Any lactide polymer composition, which comes within the scope of this invention, may be used as a film.
  • the problems of degradation, fouling, and lactide formation during melt-processing of lactide polymers are addressed through suggested ranges of molecular weights and compositional limits on impurities such as residual monomer, water and catalyst along with the use of stabilizing agents and catalyst-deactivating agents.
  • a melt-stable lactide polymer film and a process for manufacturing a melt-stable lactide polymer film from a melt-stable lactide polymer are disclosed.
  • Lactide polymers are useful due to their recycleable and biodegradable nature.
  • lactide polymers are compostable as illustrated in Example 15 below. Applicants believe the hydrolysis of the ester may be the key to or the first step in degradation of a lactide polymer composition. The mechanism of degradation is not key to the films of the present invention, however it must be recognized that such degradation makes lactide polymers desirable as replacements for presently-utilized non-degradable petrochemical-based polymers used for films.
  • Lactic acid has two optical isomers, L-lactic acid, also known as (S)-lactic acid, and D-lactic acid, also known as (R)-lactic acid.
  • Three forms of lactide can be derived from the two forms of lactic acid. They are L,L-lactide, also known as L-lactide and which comprises two (S)-lactic acid residuals; D,D-lactide, also known as D-lactide and which comprises two (R)-lactic acid residuals; and meso-lactide, which comprises one each of (R)- and (S)lactic acid residuals.
  • a 50/50 sold mixture of D-lactide and L-lactide with a melting point of about 126° C. is sometimes called D,L-lactide. At temperatures higher than the melting point, it is essentially a liquid mixture of D-lactide and L-lactide.
  • Crystallinity requires relatively long sequences of a particular residual, either long sequences of (R) or of (S).
  • the length of the interrupting sequences may be important for establishing other features of the polymer, such as the rate at which it crystallizes or the melting point of the crystalline phase, or melt processability.
  • the table below shows the expected statistical distribution of the major and minor sequence lengths assuming random polymerization and neglecting transesterification.
  • the table shows data for mixtures containing predominately the (S) configuration, the same results would be obtained for mixtures containing predominately the (R) configuration.
  • Polymers made either from L- and D-lactic acid (by direct condensation, for example) or from L-lactide with small amounts of meso-lactide have a somewhat similar structure when compared at similar levels of (S) and (R) residuals, as shown in the table above.
  • melt-processing frequently produces some proportion of trimmed or rejected material.
  • Environmental concerns and economical efficiencies dictate that this material be reused, typically by regrinding and adding back the material into the polymer feed. This introduces additional thermal stress on the polymer and increases the need for a melt-stable polymer composition.
  • the lactide polymers of the present invention are melt-stable.
  • melt-stable it is meant generally that the lactide polymer, when subjected to melt-processing techniques, adequately maintains its physical properties and does not generate by-products in sufficient quantity to foul or coat processing equipment.
  • the melt-stable lactide polymer exhibits reduced degradation and/or reduced lactide formation relative to known lactide polymers. It is to be understood that degradation will occur during melt-processing.
  • the compositional requirements and use of stabilizing agents as disclosed herein reduces the degree of such degradation to a point where physical properties are not significantly affected by melt-processing and fouling by impurities or degradation by-products such as lactide does not occur.
  • melt-stable polymer should be melt-processable in melt-processing equipment such as that available commercially. Further, the polymer will preferably retain adequate molecular weight and viscosity. The polymer should preferably have sufficiently low viscosity at the temperature of melt-processing so that the extrusion equipment may create an acceptable film. The temperature at which this viscosity is sufficiently low will preferably also be below a temperature at which substantial degradation occurs.
  • the melt-stable lactide polymer film of the present invention comprises a plurality of poly(lactide) polymer chains having a number average molecular weight from about 10,000 to about 300,000. In a preferred composition for a film, the number average molecular weight ranges from about 20,000 to about 275,000. In the most preferred composition, the number average molecular weight ranges from about 40,000 to about 250,000.
  • a film is considered to be semi-crystalline if it exhibits a net melting endotherm of greater than about 10 J/gm of poly(lactide) when analyzed by a differential scanning calorimeter DSC.
  • DSC differential scanning calorimeter
  • a suitable temperature program is to start at -20° C. and scan at 20° C./min to 200° C.
  • Typical features which may be observed include a glass transition at a temperature designated Tg, a relaxation endotherm peak immediately following Tg, a crystallization exotherm peak (generally in the range of 70°-140° C.), and a melting endotherm peak (generally in the range of 100°-200° C.).
  • Tg glass transition at a temperature designated Tg
  • a relaxation endotherm peak immediately following Tg a crystallization exotherm peak
  • a melting endotherm peak generally in the range of 100°-200° C.
  • a film is considered to be semi-crystalline if it exhibits a net melting endotherm of greater than about 10 J/gm of poly(lactide).
  • the net melting endotherm is the energy of the melting endotherm less the energy of the crystallization exotherm if present.
  • Example 9 it appears that the physical properties such as modulus, tensile strength, percentage elongation at break, impact strength, flexural modulus, and flexural strength remain statistically constant when the lactide polymer samples are above a threshold molecular weight.
  • Example 22 there is a practical upper limit on molecular weight based on increased viscosity with increased molecular weight.
  • the melt-processing temperature In order to melt-process a high molecular weight lactide polymer, the melt-processing temperature must be increased to reduce the viscosity of the polymer.
  • the exact upper limit on molecular weight must be determined for each melt-processing application in that required viscosities vary and residence time within the melt-processing equipment will also vary. Thus, the degree of degradation in each type of processing system will also vary. Based on the disclosure of Example 22, it is believed that one could determine the suitable molecular weight upper limit for meeting the viscosity and degradation requirements in any application.
  • Lactide polymers can be in either an essentially amorphous form or in a semi-crystalline form. For various applications it will be desirable to have the polymer in semi-crystalline form. Semi-crystalline films have superior heat resistance. The tendency of films to adhere together at temperatures experienced during manufacture, use, shipping or storage when on a roll or part of a product is reduced for semi-crystalline films.
  • Semi-crystalline films also have decreased permeation to gases, such as oxygen, and moisture. This is an advantage in packaging applications, especially food packaging.
  • Lactide polymer films with increased crystallinity generally degrade more slowly than amorphous films under conditions of high humidity and heat which results in extended shelf life of the films.
  • compositions for semi-crystalline poly(lactide) is less than about 15 percent by weight meso-lactide and the remaining percent by weight being either L-lactide or D-lactide, wherein at least 85 percent comprises either the L or D-lactide isomer.
  • a more preferred composition contains less than about 12 percent by weight meso-lactide and a most preferred composition has less than about 9 percent by weight meso-lactide with the remainder being substantially all L-lactide and/or D-lactide.
  • a plasticizing agent Dioctyl adipate is an example of a plasticizer which helps crystallization rates in poly(lactide), as detailed in Example 25.
  • a second method to increase the rate of crystallization is to add a nucleating agent, as detailed in Example 26.
  • a third method to induce crystallinity is to orient the polymer molecules. Orientation can be accomplished by drawing during film casting, blowing films, stretching a sheet after it is cast or blown (in multiple directions, if desired), or by the flow of polymer through a small opening in a die. When the process of orientation results in crystallization it is known as stress induced crystallization.
  • a fourth method of inducing crystallization is heat-setting, which involves holding a constrained oriented film or fiber at temperatures above Tg. It is demonstrated in Examples 27 and 33.
  • Heat setting involves exposing the film to elevated temperatures, as shown in Plastics Extrusion Technology, F. Hensen (ed), Hanser Publishers, New York, 1988, pp 308, 324. It is preferred to heat set the film under tension to reduce shrinkage during the setting process.
  • poly(lactide) having a meso-content of less than about 12% may be drawn just above its Tg in a machine direction orientation (MDO) or transverse direction orientation (TDO) process to increase the degree of crystallinity.
  • MDO machine direction orientation
  • TDO transverse direction orientation
  • the sheet may be drawn at room temperature to increase levels of crystallinity from less than 5 J/gm to greater than 15 J/gm.
  • Example 31 demonstrates the increase in crystallinity of a plasticized poly(lactide) sheet upon drawing. The properties of the crystallized and plasticized film are superior with regard to flexible film over non crystallized film.
  • Crystallizing a plasticized film increases the blocking temperature of the film as shown in Example 32.
  • the tensile strength and barrier properties will also increase upon crystallization.
  • Crystallizing lactide polymer films may be performed by drawing the film in either the machine direction or transverse direction or in both directions using draw ratios of 1.1 or greater. The temperature of the draw rolls are generally set at temperatures at or slightly above the Tg of the film.
  • the degree of crystallinity in lactide polymer films containing at least 15% plasticizer may also be increased by storing the film at room temperature until levels of crystallinity greater than 10 J/g is reached. Storing the film under elevated temperatures may increase the rate of crystallization, especially in lactide polymer films containing less than 15% plasticizer.
  • Crystallization of the lactide polymer may also be done during the manufacture of resin pellets.
  • the crystalline portions of the polymer are melted during film manufacture, therefore recrystallization during film manufacture is still required from semi-crystalline films.
  • crystalline resin pellets may be dried at higher temperatures, therefore faster than amorphous resin pellets due to the increased resistance of semi-crystalline resin pellets to adhere together at elevated temperatures. Crystallization of the resin pellets may be done by drawing the strand of polymer to a draw ratio of at least 1.1 as it exits the extruder and prior to being pelletized.
  • Crystallinity may also be increased in lactide polymers containing at least 15% plasticizer by storing the pellets at room temperature for a period of time necessary to increase crystallinity above 10 Joules per gram.
  • Crystalline poly L-lactide exhibits an endotherm of roughly 92 joules per gram at its melting temperature of 170°-190° C., as shown by S. Gogolewski and A. J. Pennings, J. Applied Polymer Science, Vol. 28, pp 1045-1061 (1983). The melting point changes with composition. The degree of crystallinity is roughly proportional to the endotherm on melting.
  • semi-crystalline poly(lactide) exhibits a net melting endotherm above about 10 joules per gram of poly(lactide).
  • an amorphous or non-crystalline poly(lactide) is a poly(lactide) or lactide polymer which exhibits a net melting endotherm of less than about 10 joules per gram of poly(lactide) in the temperature range of about 100°-200° C.
  • the molecular weight of a polymer sample can be determined through the use of gel permeation chromatography (GPC).
  • GPC gel permeation chromatography
  • the GPC analysis was conducted with an Ultrastyragel® column from Waters Chromatography.
  • the mobile phase was chloroform.
  • a refractive index detector with molecular weight calibration using polystyrene standards was used.
  • the GPC temperature was 35° C.
  • Molecular weights were determined by integrating from the highest molecular weight fraction down to 4,000 amu. The region below 4,000 amu is excluded from the calculations of molecular weight in order to improve reproducibility of the number average molecular weight. This material may be separately reported as "oligomers" and residual lactide, as in Example 11.
  • the residual monomer concentration in the melt-stable lactide polymer composition is less than about 2.0 percent by weight.
  • the lactide concentration is less than about 1.0 percent by weight and a most preferred composition has less than about 0.5 percent by weight of lactide.
  • the monomer cannot be used as a plasticizing agent in the resin of the present invention due to significant fouling of the extrusion equipment. As detailed in Example 16, it is believed the low levels of monomer concentration do not plasticize the final polymer.
  • the water concentration within the melt-stable lactide polymer composition is less than about 2,000 parts-per-million. Preferably this concentration is less than 500 parts-per-million and most preferably less than about 100 parts-per-million.
  • the polymer melt-stability is significantly affected by moisture content.
  • the melt-stable polymer of the present invention must have the water removed prior to melt-processing.
  • water concentration may be reduced prior to processing the polymerized lactide to a resin.
  • moisture control could be accomplished by packaging such resins in a manner which prevents moisture from contacting the already-dry resin.
  • the moisture content may be reduced at the melt-processor's facility just prior to the melt-processing step in a dryer.
  • Example 14 details the benefit of drying just prior to melt-processing and also details the problems encountered due to water uptake in a polymer resin if not stored in a manner in which moisture exposure is prevented or if not dried prior to melt-processing. As detailed in these examples, Applicants have found that the presence of water causes excessive loss of molecular weight which may affect the physical properties of the melt-processed polymer.
  • a stabilizing agent is included in the polymer formulation to reduce degradation of the polymer during production, devolatilization, drying and melt processing by the end user.
  • the stabilizing agents recognized as useful in the present films may include antioxidants and/or water scavengers.
  • Preferred antioxidants are phosphite-containing compounds, hindered phenolic compounds or other phenolic compounds.
  • the antioxidants include such compounds as trialkyl phosphites, mixed alkyl/aryl phosphites, alkylated aryl phosphites, sterically hindered aryl phosphites, aliphatic spirocyclic phosphites, sterically hindered phenyl spirocyclics, sterically hindered bisphosphonites, hydroxyphenyl propionates, hydroxy benzyls, alkylidene bisphenols, alkyl phenols, aromatic amines, thioethers, hindered amines, hydroquinones and mixtures thereof.
  • many commercially-available stabilizing agents have been tested and fall within the scope of the present melt-stable lactide polymer film. Biodegradable antioxidants are particularly preferred.
  • the water scavengers which may be utilized in preferred embodiments of the melt-stable lactide polymer film include: carbodiimides, anhydrides, acyl chlorides, isocyanates, alkoxy silanes, and desiccant materials such as clay, alumina, silica gel, zeolites, calcium chloride, calcium carbonate, sodium sulfate, bicarbonates or any other compound which ties up water.
  • the water scavenger is degradable or compostable.
  • Example 19 details the benefits of utilizing a water scavenger.
  • a plasticizer is included in the polymer formulation to improve the film quality of the lactide polymer. More particularly, plasticizers reduce the melt viscosity at a given temperature of poly(lactide), which assists in processing and extruding the polymer at lower temperatures and may improve flexibility and reduce cracking tendencies of the finished film and also improves impact and tear resistance of the film and decreases noise.
  • a plasticizer is useful in concentration levels of about 1 to 40 percent based on weight of polymer. Preferably, a plasticizer is added at a concentration level of about 5 to 25 percent. Most preferably, a plasticizer is added at a concentration level of about 8 to 25 percent.
  • plasticizing agent requires screening of many potential compounds and consideration of several criteria.
  • the preferred plasticizer is to be biodegradable, non-toxic and compatible with the resin and relatively nonvolatile.
  • Plasticizers in the general classes of alkyl or aliphatic esters, ether, and multi-functional esters and/or ethers are preferred. These include alkyl phosphate esters, dialkylether diesters, tricarboxylic esters, epoxidized oils and esters, polyesters, polyglycol diesters, alkyl alkylether diesters, aliphatic diesters, alkylether monoesters, citrate esters, dicarboxylic esters, vegetable oils and their derivatives, and esters of glycerine. Most preferred plasticizers are tricarboxylic esters, citrate esters, esters of glycerine and dicarboxylic esters. Citroflex A4® from Morflex is particularly useful. These esters are anticipated to be biodegradable. Plasticizers containing aromatic functionality or halogens are not preferred because of their possible negative impact on the environment.
  • suitable non-toxic character is exhibited by triethyl citrate, acetyltriethyl citrate, tri-n-butyl citrate, acetyltri-n-butyl citrate, acetyltri-n-hexyl citrate, n-butyltri-n-hexyl citrate and dioctyl adipate.
  • Appropriate compatibility is exhibited by acetyltri-n-butyl citrate and dioctyl adipate.
  • Other compatible plasticizers include any plasticizers or combination of plasticizers which can be blended with poly(lactide) and are either miscible with poly(lactide) or which form a mechanically stable blend. Corn oil and mineral oil were found to be incompatible when used alone with poly(lactide) because of phase separation (not mechanically stable) and migration of the plasticizer.
  • Volatility is determined by the vapor pressure of the plasticizer.
  • An appropriate plasticizer must be sufficiently non-volatile such that the plasticizer stays substantially in the resin formulation throughout the process needed to produce the film. Excessive volatility can lead to fouling of process equipment, which is observed when producing films by melt processing poly(lactide) with a high lactide content.
  • Preferred plasticizers should have a vapor pressure of less than about 10 mm Hg at 170° C., more preferred plasticizers should have a vapor pressure of less than 10 mm Hg at 200° C. Lactide, which is not a preferred plasticizer, has a vapor pressure of about 40 mm Hg at 170° C.
  • Example 6 highlights useful plasticizers for the present invention.
  • Epoxides provide one method of introducing an internal plasticizer.
  • nucleating agents may be incorporated during polymerization.
  • Nucleating agents may include selected plasticizers, finely divided minerals, organic compounds, salts of organic acids and imides and finely divided crystalline polymers with a melting point above the processing temperature of poly(lactide).
  • useful nucleating agents include talc, sodium salt of saccharin, calcium silicate, sodium benzoate, calcium titanate, boron nitride, copper phthalocyanine, isotactic polypropylene, crystalline poly(lactide) and polybutylene terephthalate.
  • fillers may be used to prevent blocking or sticking of layers or rolls of the film during storage and transport.
  • Inorganic fillers include clays and minerals, either surface modified or not. Examples include talc, diatomaceous earth, silica, mica, kaolin, titanium dioxide, perlite, and wollastonite. Preferred inorganic fillers are environmentally stable and non-toxic.
  • Organic fillers include a variety of forest and agricultural products, either with or without modification. Examples include cellulose, wheat, starch, modified starch, chitin, chitosan, keratin, cellulosic materials derived from agricultural products, gluten, nut shell flour, wood flour, corn cob flour, and guar gum. Preferred organic fillers are derived from renewable sources and are biodegradable. Fillers may be used either alone or as mixtures of two or more fillers. Examples 4 and 5 highlight useful anti-blocking fillers for the present invention. Surface treatments such as corona and flame treatments may also be used to reduce blocking.
  • Pigments or color agents may also be added as necessary. Examples include titanium dioxide, clays, calcium carbonate, talc, mica, silica, silicates, iron oxides and hydroxides, carbon black and magnesium oxide.
  • tin(II) bis(2-ethyl hexanoate) commercially available from Atochem, as Fascat 2003, and Air Products as DABCO T-9
  • dibutyltin diacetate Fascat 4200®, Atochem
  • butyltin tris(2-ethyl hexanoate) Fascat 9102®, Atochem
  • hydrated monobutyltin oxide Fascat 9100®, Atochem
  • antimony triacetate S-21, Atochem
  • antimony tris(ethylene glycoxide) S-24, Atochem.
  • tin(II) bis(2-ethyl hexanoate) butyltin tris(2-ethyl hexanoate) and dibutyltin diacetate appear to be most effective.
  • Example 10 details the effect of residual catalyst on degradation.
  • the residual catalyst level in the resin is present in a molar ratio of initial monomer-to-catalyst greater than about 3,000:1, preferably greater than about 5,000:1 and most preferably greater than about 10,000:1.
  • Applicants believe a ratio of about 20,000:1 may be used, but polymerization will be slow. Optimization of catalyst levels and the benefits associated therewith are detailed in Example 20.
  • catalyst concentration may be reduced subsequent to polymerization by precipitation from a solvent.
  • Example 21 demonstrates potential catalyst removal by precipitation from a solvent. This produces a resin with reduced catalyst concentration.
  • the catalyst means for catalyzing the polymerization of lactide to form the poly(lactide) polymer chains which was incorporated into the melt-stable lactide polymer composition during polymerization is deactivated by including in the melt-stable lactide polymer composition a catalyst deactivating agent in amounts sufficient to reduce catalytic depolymerization of the poly(lactide) polymer chains.
  • Example 11 details the benefits of utilizing a catalyst deactivating agent.
  • Such catalyst-deactivating agents include hindered, alkyl, aryl and phenolic hydrazides, amides of aliphatic and aromatic mono- and dicarboxylic acids, cyclic amides, hydrazones and bishydrazones of aliphatic and aromatic aldehydes, hydrazides of aliphatic and aromatic mono- and dicarboxylic acids, bis-acylated hydrazine derivatives, and heterocyclic compounds.
  • a preferred metal deactivator is Irganox® MD1024 from Ciba-Geigy. Biodegradable metal deactivators are particularly preferred.
  • the catalyst concentration is reduced to near zero by utilizing a solid-supported catalyst to polymerize lactide.
  • a solid-supported catalyst to polymerize lactide.
  • the feasibility of utilizing such a catalyst is detailed in Example 8. It is believed catalysts which may be utilized include supported metal catalysts, solid acid catalysts, acid clays, alumina silicates, alumina, silica and mixtures thereof.
  • the catalyst usage and/or deactivation is controlled to reduce depolymerization of the poly(lactide) polymer during melt-processing to less than about 2 percent by weight generation of lactide from a devolatilized sample in the first hour at 180° C. and atmospheric pressure. More preferably, the amount of lactide generated is less than about 1 percent by weight in the first hour and most preferably less than about 0.5 percent by weight in the first hour.
  • a preferred melt-stable lactide polymer composition is the reaction product of polymerization of lactide at a temperature greater than about 160° C. Applicants have found that polymerization at higher temperatures result in a characteristically different polymer which is believed to have improved melt stability due to increased transesterification during polymerization. The benefits of higher temperature polymerization are detailed in Example 12.
  • the process for the manufacture of a melt-stable lactide polymer comprises the steps of first providing a lactide mixture wherein the mixture contains less than 15 percent by weight meso-lactide with the remainder being L-lactide and/or D-lactide.
  • Such purified lactide stream may be such as that produced in the process disclosed by Gruber et al., although the source of lactide is not critical to the present invention.
  • the lactide mixture is polymerized to form a lactide polymer or poly(lactide) with some residual unreacted monomer in the presence of a catalyst means for catalyzing the polymerization of lactide to form poly(lactide).
  • Catalysts suitable for such polymerization have been listed previously.
  • concentration of catalysts utilized may be optimized as detailed in the following examples and discussed previously.
  • a stabilizing agent which may be an antioxidant and/or a water scavenger is added to the lactide polymer. It is recognized that such stabilizing agents may be added simultaneously with or prior to the polymerization of the lactide to form the lactide polymer. The stabilizing agent may also be added subsequent to polymerization. As previously disclosed, the catalyst usage is adjusted and/or deactivation agent is added in a sufficient amount to reduce depolymerization of poly(lactide) during melt-processing to less than 2 percent by weight generation of lactide from a devolatilized sample in the first hour at 80° C. and atmospheric pressure.
  • the stabilizing agent controls lactide generation to less than 1 percent by weight and most preferably less than 0.5 percent by weight in the first hour at 180° C., and atmospheric pressure.
  • the control of catalyst concentration to optimize the balance between necessary catalytic activity to produce poly(lactide) versus the detrimental effects of catalytic depolymerization or degradation of the lactide polymer may be utilized to obviate the need for adding a stabilizing agent.
  • the lactide polymer is then devolatilized to remove unreacted monomer which may also be a by-product of decomposition reactions or the equilibrium-driven depolymerization of poly(lactide). Any residual water which may be present in the polymer would also be removed during devolatilization, although it is recognized that a separate drying step may be utilized to reduce the water concentration to less than about 2,000 parts-per-million.
  • the devolatilization of the lactide polymer may take place in any known devolatilization process.
  • the key to selection of a process is operation at an elevated temperature and usually under conditions of vacuum to allow separation of the volatile components from the polymer. Such processes include a stirred tank devolatilization or a melt-extrusion process which includes a devolatilization chamber and the like. An inert gas sweep is useful for improved devolatization.
  • the process also includes the step of adding a molecular weight control agent to the lactide prior to catalyzing the polymerization of the lactide.
  • molecular weight control agents include active hydrogen-bearing compounds, such as lactic acid, esters of lactic acid, alcohols, amines, glycols, diols and triols which function as chain-initiating agents.
  • Such molecular weight control agents are added in sufficient quantity to control the number average molecular weight of the poly(lactide) to between about 10,000 and about 300,000.
  • FIG. 1 illustrates a preferred process for producing a melt-stable lactide polymer composition.
  • a mixture of lactides enters a mixing vessel (3) through a pipeline (1).
  • a catalyst for polymerizing lactide is also added through a pipeline (13).
  • a stabilizing agent may be added through a pipeline (2).
  • a water scavenger may also be added through the pipeline (2).
  • the stabilized lactide mixture is fed through a pipeline (4) to a polymerization process (5).
  • the polymerized lactide or lactide polymer leaves the polymerization process through a pipeline (6).
  • the stream is fed to a second mixing vessel (8) within which a stabilizing agent and/or catalyst deactivating agent may be added through a pipeline (7).
  • the stabilized lactide polymer composition is then fed to a devolatilization process (10) through a pipeline (9). Volatile components leave the devolatilization process through a pipeline (11) and the devolatilized lactide polymer composition leaves the devolatilization process (10) in a pipeline (12).
  • the devolatilized lactide composition is fed to a resin-finishing process (14). Within the resin-finishing process the polymer is solidified and processed to form a pelletized or granular resin or bead. Applicants recognize the polymer may be solidified and processed to form resin or bead first, followed by devolatilization.
  • the resin is then fed to a drying process (16) by conveyance means (15).
  • the dried lactide polymer resin leaves the drying process (16) by a conveyance means (18) and is fed to a melt-processing apparatus (19). Within the melt-processing apparatus (19) the resin is converted to a useful article as disclosed above. The useful article leaves the melt-processing apparatus (19) through a conveyance means (20).
  • Polycaprolactone commercially available as TONE 787 from Union Carbide was added/mixed with poly(lactide) having a number average molecular weight of 157,900, a residual lactide concentration of 0.19%, a meso-lactide concentration of about 10% and a water concentration of less than about 500 ppm on a Leistritz twin screw extruder at 12.8%, 25.6%, 38.4% by weight to poly(lactide).
  • These blends were injection molded into standard ASTM test bars using a Cincinnati Milacron Vista Sentry VST-55 molding press and physical properties were measured and tensiles tested on the bars.
  • the above blends were also extruded into cast film on a Killion extruder with a sheet die, die gap 0.035", with 0.25% by weight Celite Super Floss diatomaceous earth for the purpose of an anti-block agent.
  • the polymer selected had a 280,000 to 400,000 weight average molecular weight, a 100,000 to 150,000 number average molecular weight, lactide concentration lower than 1%, meso level of about 10 to 20%, and a moisture level lower than about 500 ppm.
  • the sheet was cast using a 2" diameter single barrier flight screw Davis-Standard extruder with a 24:1 L/D.
  • the die was 24" wide with an adjustable gap.
  • the casting roll was 30" wide and 24" in diameter and equipped with temperature controls. After casting, the sheet was oriented in both the machine (MD) and transverse (TD) directions.
  • the MD orienter consisted of six 30" wide rolls and five temperature control zones: roll 1 and 2 were for preheat, roll 3 for slow draw, roll 4 for fast draw, roll 5 for heat setting, and roll 6 for cooling the sheet. Draw ratios up to 20 were used for the MD orientation.
  • the TD was a standard tenter frame with a 3 zone oven.
  • the feed width range for the tenter was 8-48" and the output width range was 16-62".
  • Following the orientation section was a slitter/winder.
  • Melt strength at the die was very good at 330° F. (166° C.).
  • the die was positioned about 0.5 inch off the cast roll, which was run between 112 and 126° F.
  • An air knife was used to pin the melt against the cast roll to reduce neck-in.
  • Conditions found useful for machine direction orientation of poly(lactide) were temperatures of 65° C. for the preheat rolls, 65° C. and 72° C. for the slow draw roll at low draw ratios and high draw ratios respectively, 65° C. for the fast draw roll, 45° C. for the heat roll, and 20° C. for the cooling roll.
  • the gap between the slow and fast roll was set to the minimum possible. Orientation took place only slightly above the Tg to give a high degree of molecular alignment. Rolls were collected after MD orientation and some were used for TD orientation. Conditions for transverse direction orientation were 63° C. for the preheat zone, 70° C. for the stretching zone, and 67° C. for the annealing zone. Ambient air was circulated at the oven exit to cool the oriented sheet before winding. The poly(lactide) oriented very well, being easily curved over the rolls and requiring lower process temperatures than standard plastic. The products made were:
  • the tensile strength and flexibility of the poly(lactide) film can be greatly increased by orientation.
  • Poly(lactide) having a weight average molecular weight of 165,000, a meso level of about 6%, a lactide level of less than about 0.2%, and a moisture level of less than about 500 ppm was blended with 25% by weight acetyl tributylcitrate (Citroflex A4 from Morflex) in a Werner & Pfleiderer twin screw extruder.
  • Two films of this composition were prepared in a Carver press equipped with heated platens at a temperature of 300°-350° F. and a dwell time of about 60 seconds. These films were annealed in an oven over four days to induce crystallization of the poly(lactide) samples. The films were tested for resistance to blocking at an elevated temperature. This test was performed by placing two films in contact with each other in an oven held at 60° C. with a 95 gram weight with a surface area of about 2.5 in 2 on top of the two films. After more than four hours, the films were removed from the oven and any adhesion between the films was noted. No adhesion occurred during the test. Prior to the annealing and crystallization procedure, films adhered to one another at room temperature.
  • anti-block aids can increase the resistance of two poly(lactide) films to stick together at elevated temperatures. This was demonstrated using poly(lactide) having a weight molecular weight of 165,000, a residual lactide level of about 0.1%, a meso level of about 10%, and a moisture level of about 60 ppm.
  • the anti-block aid was diatomaceous earth having a median particle size of 3.5 microns (Celite Super Floss from Celite) which was dried to a moisture level of about 400 ppm.
  • the diatomaceous earth and poly(lactide) were blended in a twin screw extruder at different levels of anti-block aid and pelletized. The pellets were converted into film using the single screw extruder as in example 2.
  • the films were tested for resistance to adhering to one another by placing two films together with a 92 gram weight on top in an oven set at 60° C. for 2 hours. A failure was when the films could not be separated after being removed from the oven. The results are shown in the table below:
  • Dried pellets of devolatilized poly(lactide) were processed in a twin screw extruder to allow compounding of various plasticizing agents.
  • the strands leaving the extruder were cooled in a water trough and chopped into pellets.
  • Samples of the pellets were heated at 20° C./minute to 200° C. in a DSC apparatus, held at 200° C. for 2 minutes and rapidly cooled to quench the samples.
  • the quenched samples were then reheated in the DSC apparatus increasing at 20° C./minute to determine the glass transition temperature.
  • These samples were compared to a polymer with no plasticizer.
  • the effect of the plasticizer on the glass transition temperature is shown in the table below. Glass transition temperatures are taken at the mid-point of the transition.
  • A-4 is the designation of a purified acetyltri-n-butyl citrate.
  • A-2 is the designation of acetyltriethyl citrate,
  • A-6 is the designation of acetyltri-n-hexyl citrate, and
  • B-6 is the designation of n-butyryltri-n-hexyl citrate.
  • Poly(lactide) samples with various molecular weights and optical compositions were prepared by polymerizing blends of L-lactide and meso-lactide at 180° C. under nitrogen in a 1-gallon sealed reactor.
  • Tin(II) bis(2-ethyl hexanoate) catalyst was added at a monomer-to-catalyst ratio of 10,000:1. After about 1 hour the molten polymer was drained from the reactor using nitrogen pressure. The sample was poured into a pan and placed in a vacuum oven at about 160° C. for about 4 hours to bring the reaction to near equilibrium levels.
  • test bars Samples of the test bars after injection molding were analyzed by GPC for molecular weight. Other portions of the test bars were reground and tested in a capillary viscometer to determine the melt-viscosity. These results are also included in Table 8.
  • the viscosity data show significant correlations with molecular weight. This dependence documents the practical limitation and necessity of controlling polymer molecular weight below an upper limit at which it is impractical to melt-process the polymer. At high molecular weight, high viscosity prevents processing by standard melt-processing equipment. Increases in temperature to reduce viscosity dramatically increase polymer degradation and lactide formation which is also unacceptable.
  • Polymer samples were prepared at four levels of catalyst, corresponding to monomer to catalyst molar ratios of 5,000:1, 10,000:1, 20,000:1, and 40,000:1.
  • the catalyst utilized was tin (II) bis(2-ethyl hexanoate). These samples were then subjected to heating in a TGA apparatus (TA Instruments, Inc., model 951 thermogravometric analyzer with a DuPont 9900 computer support system) with a nitrogen purge. Isothermal conditions of 200° C. for 20 minutes were used.
  • the samples were then analyzed by GPC with a viscosity-based detector and a universal calibration curve to determine the extent of breakdown in molecular weight.
  • the GPC apparatus for this test was a Viscotek Model 200 GPC and a Phenomenex column.
  • the TGA analysis typically resulted in about a 5 percent loss in weight and molecular weight drops of 0 to 70 percent.
  • the number average molecular weights were converted to a milliequivalent per kilogram basis (1,000,000/Mn) in order to calculate a rate of chain scission events.
  • the results below represent averages of 2-4 replicates on each of the four samples.
  • Lactide feed was 80 percent L-lactide and 20 percent D,L-lactide.
  • Molecular weight was controlled by adding a small quantity of lactic acid, the target molecular weight was 80,000 Mn.
  • Lactide was charged to the reactor as a dry mix, the reactor was purged 5 times with nitrogen, and heated up to 180° C. At this point catalyst (5000:1 initial monomer to catalyst molar ratio, Fascat®2003) was charged through a port in the top of the reactor. The reaction was allowed to proceed for 70 minutes at 180° C., with mechanical agitation. Conversion at this point was 93-94 percent, close to the equilibrium value at 180° C. of 96 percent poly(lactide) from FIG. 2. This point is considered t-zero, designating the completion of the polymerization reaction and the beginning of the mixing time. In the control experiment, a sample was taken and the mixture was held at temperature with continued agitation. Samples were taken periodically through a port in the reactor bottom.
  • the reactor was drained.
  • a sample was taken and 0.25 weight percent of a metal deactivator (Irganox® MD 1024®) was added through the catalyst addition port. The mixture was held at temperature with continued agitation and samples were withdrawn periodically. The reactor was drained after 4 hours.
  • a metal deactivator Irganox® MD 1024®
  • GPC analysis (utilizing the method of Example 7) for these samples was divided into three parts: polymer with molecular weight over 4,000 (for which the Mn and Mw numbers are reported), the percent oligomers (comprising the region with molecular weight greater than lactide but less than 4,000, as distinguished from oligomers as defined by Loomis to include only oligomers up to a molecular weight of 450), and percent lactide (residual monomer).
  • the structure of the oligomers was not certain, but it is believed they were primarily cyclic structures. It is also believed that the metal deactivator, if unreacted, will elute with the oligomer fraction. Quantification of the oligomer fraction is difficult, because the GPC trace is near the baseline in this region.
  • Equilibrium lactide levels are estimated to be less than 0.2 weight percent at room temperature. Consistent with that, essentially no lactide was observed in any of the samples (detection limit about 0.1 weight percent).
  • the oligomer content in the non-stabilized samples declined and some increase in molecular weight was noted, perhaps due to reincorporation of the (cyclic) oligomers into the polymer.
  • the oligomer depletion reaction was inhibited in the stabilized polymers, with the extent of inhibition dependent on the length of time that the additive was mixed.
  • the data for molecular weight show that if the metal deactivator is not mixed into the system long enough then it can have a detrimental impact on stability in the melt.
  • the samples for which the mixing was at least 1.5 hours show no detrimental effect, and the 4 hour sample appears to be somewhat more stable than any of the others based on molecular weight alone. More importantly, the metal deactivator samples show significantly less lactide reformation than the control samples. This effect is gained even in the samples which were mixed for only 0.5 hour.
  • the metals deactivated samples averaged only 1.8 percent lactide after one hour at 180° C., compared to an average of 3.0 percent lactide for the controls. The equilibrium level at 180° C. is about 3.6 percent from FIG. 2.
  • the use of metal deactivators can reduce the troublesome reformation of lactide during melt-processing of the finished polymer.
  • L-lactide (Boeringer Ingleheim, S-grade) was used as received, meso-lactide (PURAC) was purified by distillation to remove traces of D- and L-lactide. The melting point of the purified meso-lactide was 54° C. Lactide mixtures were made up to the following ratios: 100 percent L-lactide, 90/10 L-lactide/meso-lactide, 70/30 L-lactide/meso-lactide, 50/50 L-lactide/meso-lactide, and 100 percent meso-lactide.
  • Catalyst level was 2,500:1 molar ratio of initial monomer to tin with the tin being tin(II) bis (2-ethyl hexanoate) (Fascat® 9002). Lactic acid was added as a molecular weight control agent to target a number average molecular weight of 50,000 (the same amount was added to all samples). Polymerization times were estimated to obtain conversions of 50 percent and 90 percent. For 120° C. this was 4 hours and 16 hours, respectively. For 180° C. these times were 10 minutes and 50 minutes, respectively. Below in Table 14 are the GPC results (method of Example 7) of tests on the polymer samples produced by this procedure.
  • vial polymerization (Lactide is melted under a nitrogen-purged atmosphere in a round bottom flask with stirring. Catalyst and additives are added and aliquots of the mixtures are pipetted into silanized glass vials. Typically 5-10 grams of reaction mixture are used in a 16 ml. vial. The vials are tightly capped and placed into a preheated oil bath.) 10,000:1 molar ratio of lactide-to-tin, tin(II) bis(2-ethyl hexanoate) catalyst, 0.2 wt percent Ultranox®626 in tetrahydrofuran (THF). 180° C. Time was 90 minutes.
  • control sample turned light yellow, the sample with stabilizer remained colorless.
  • the sample with phosphite stabilizer again polymerized faster and went to a higher molecular weight than the non-stabilized sample.
  • the phosphite stabilized sample had a molecular weight more than 60% higher than the control for all time periods.
  • the phosphite-stabilized sample had a molecular weight more than 60 percent higher than the control for all time periods. After 72 hours it had a molecular weight 2.8 times higher than the control. The sample with antioxidant showed an initial increase in molecular weight, relative to the control, but the effect disappeared after 48 hours. The phosphite stabilized sample was significantly lighter in color than the control or the antioxidant treated sample.
  • the phosphites and the phenolic antioxidants provide increased molecular weight with no reduction in polymerization rate.
  • Naugard® 445 provided stabilization without a rate decrease.
  • the metal deactivators are expected to deactivate the catalyst, as was observed for Irganox® MD1024.
  • the Naugard® XL-1 did not accomplish deactivation.
  • Lactide, produced and purified in a continuous (Gruber et al.) process was fed at a rate of 3 kg/hr to a continuous polymerization pilot plant. Catalyst was added with a metering pump at the rate of 1 part catalyst to 5000 parts lactide on a molar basis. The reaction system was blanketed with nitrogen.
  • the reactor vessels consist of two continuous stirred tank reactors (CSTR) in series. The first had a 1-gallon capacity and the second had a 5-gallon capacity. The reactors were run 60°-80 percent liquid filled and at 170°-180° C. Polymer melt pumps moved the liquid from CSTR 1 to CSTR 2, and from CSTR 2 through a die into a cooling water trough. The polymer strand thus produced was pulled from the trough by a pelletizer and stored as pellets.
  • CSTR continuous stirred tank reactors
  • the pelletized poly(lactide) was put into a drying hopper and dried at 40° C. under flowing dry air. Samples were pulled after one hour and four hours. These samples were then run through a single screw Brabender® extruder, with a retention time of approximately 3 minutes. Samples were analyzed for moisture by an automatic Karl Fischer apparatus and for molecular weight by GPC (the method of Example 7). The results of these tests are documented in Table 19 below.
  • amorphous poly(lactide) sample (clear, and less than 1 percent crystallinity based on DSC) and a crystalline poly(lactide) sample (opaque, and approximately 50 percent crystallinity based on DSC) were subjected to biodegradation in a compost test (50° C., with aeration).
  • the DSC apparatus was a TA Instruments, Inc., model 910 differential scanning calorimeter with DuPont 9900 computer support system typically programmed to heating at a rate of 10° C. per minute to 200° C.
  • the samples had different optical composition, with the crystalline sample being more than 90 percent poly(L-lactide) and the amorphous sample being less than 80 percent poly(L-lactide) with the balance being either poly(D,L-lactide) or poly(meso-lactide).
  • Samples of each polymer were subjected to a compost test (ASTM D 5338) which included mixing a stabilized compost and providing a source of humidified air while maintaining a temperature of about 50° C.
  • the amorphous sample was completely degraded after 30 days of composting.
  • the crystalline sample was only 23 percent degraded based on carbon dioxide after the same period of time.
  • Poly(lactide) was precipitated in methanol from a chloroform solution in order to remove the residual lactide monomer.
  • GPC analysis (the method of Example 1) showed the precipitated polymer to contain 0.0 percent lactide.
  • the polymer was dissolved in chloroform to make a 10 wt percent solution, and lactide was added back to make 5 separate solutions which, after removing the chloroform, are calculated to produce films containing 0.0, 0.2, 0.4, 1.0 and 4.0 weight percent lactide in poly(lactide). These solutions were solvent cast onto glass, dried overnight at room temperature in a fume hood, and removed to a vacuum oven. The films were hung in the vacuum oven and dried at 30° C. for 72 hours. GPC analysis of the vacuum-dried films showed measured lactide levels of 0.0, 0.0, 0.4, 0.7 and 3.7 wt percent.
  • melt stability is as follows:
  • a small sample (200 grams or less) of polymer is ground or pelletized and devolatilized by holding under vacuum (about 10 mm Hg) at a temperature of 130° C. or less for 18 hours. At this point the residual lactide content should be 1 wt percent or less.
  • Portions (1-5 grams) of the devolatilized sample are then placed in a 16 ml sample vial, tightly capped, and placed in a 180° C. oil bath. Samples are removed at times of 15 minutes and 1 hour and analyzed for lactide content by GPC or other appropriate techniques. Lactide which may collect on the cooler portions of the vial is included in the product work-up and test.
  • Melt-stabilized poly(lactide) will show less than 2 percent lactide in the 15 minute sample, and more preferably less than 2 percent lactide in the 1 hour sample.
  • the most highly stabilized poly(lactide)s will maintain lactide contents of less than 1 percent in both the 15 minute and 1 hour samples, preferably less than 0.5 percent.
  • An unstabilized poly(lactide) may reach the equilibrium lactide content at 180° C. of 3.6 wt percent, or may go even higher as lactide is driven from the polymer melt and collects on the cooler top walls of the vial.
  • Dried poly(lactide) pellets were processed in a twin screw extruder to devolatilize and to prepare a portion with 0.5 percent by weight of a water scavenger (Stabaxol® P). The strands leaving the extruder are cooled in a water trough and chopped into pellets. Samples of the control and the test sample were then analyzed by the Karl Fischer technique for moisture content, with no drying. The control sample contained 1700 ppm water, the test sample had 450 ppm water. The control sample was then dried under nitrogen at 40° C., reducing the water content to 306 ppm. A vacuum-dried control sample had 700 ppm water.
  • test sample and the dried control samples were then processed in a 1/2" single screw extruder (Brabender®) at 160° C., with a retention time of 3 minutes.
  • the number average molecular weight for the dried control sample dropped from an initial value of 44,000 to a final value of 33,000 for the 306 ppm water sample and to 28,000 for the 700 ppm water sample.
  • the test sample number average molecular weight dropped from an initial value of 40,000 to a final value of 33,000.
  • a mixture of 80 percent L-lactide and 20 percent D,L-lactide was polymerized using three different levels of tin(II) bis(2-ethyl hexanoate) catalyst. Batches were prepared at initial monomer/catalyst molar ratios of 1000:1, 3000:1, and 20,000:1. Polymerization times were adjusted to reach high conversion without being excessively long and thereby causing degradation in the melt. The reaction times were 1,2 and 20 hours, respectively.
  • the polymerization temperature was 180° C.
  • the polymers were ground to a coarse powder and devolatilized at 125° C. and 10 mm Hg overnight.
  • the samples were then reground and 1-gram portions of each were placed into silanized vials, 16 ml capacity.
  • the vials were sealed and placed into an oil bath at 180° C. Vials were then removed at various times and the samples were analyzed by GPC after dissolution in chloroform. The molecular weights and lactide contents are shown
  • the vials were allowed to cool and the polymer recovered by breaking the glass.
  • the polymer was ground to a coarse powder and dissolved in chloroform to make a 10 percent solution.
  • the polymer contained 3.8 percent residual monomer and had a number average molecular weight of 70,000 as determined by GPC measurement (the method of Example 7).
  • the polymer consisted of a fibrous mat. It contained 0.3 percent residual monomer and had a number average molecular weight of 66,900.
  • the measured tin level in the precipitated polymer was 337 ppm by weight, compared to a calculated value of 466 ppm for the as-produced polymer. This result indicates the feasibility of reducing residual catalyst levels in lactide polymers by solvent precipitation with the benefit of improved stability as detailed in Example 20.
  • Polymer samples of various optical compositions were prepared by polymerizing mixtures of L-lactide and meso-lactide with tin(II)bis(2-ethyl hexanoate) catalyst at a temperature of about 180° C. A portion of each sample was tested in a Mettler Differential Scanning Calorimeter (DSC), Model 30, by heating from 60° C. to 200° C. at 20° C./minute. The sample was then held at 200° C. for 2 minutes to completely melt any crystals. The samples were then quenched to the annealing temperature of interest and held minutes. The samples were then quenched to 60° C. and reheated at 20° C./minute to 200° C. to determine the crystallinity. The crystallinity of the sample following annealing is proportional to the energy of the melting endotherm minus any crystallization exotherm.
  • Samples of devolatilized poly(lactide) of varying optical composition and with number average molecular weights in the range of 50,000 to 130,000 were prepared in a continuous pilot plant.
  • the samples were dissolved in chloroform to a concentration of 5 grams/100cc and the optical rotation of the samples was measured to determine the concentration of meso-lactide which had been present in the monomer mixture prior to polymerization.
  • Separate optical rotation and gas chromatography analysis of the monomer mixture confirmed that L-lactide and meso-lactide are the predominate components when meso-lactide is present at a concentration of 20 percent or less, and only a small correction is required for D-lactide.
  • the annealing procedure consisted of placing the samples in an oven at 100°-105° C. for 90 minutes, then lowering the temperature 10° C. each 1/2 hour until the temperature reached 45° C. The oven was then shut off and the samples were allowed to cool to room temperature. The energy of the melting endotherm and the peak melting temperature were then measured using a Mettler Differential Scanning Calorimeter (DSC) apparatus with a scan speed of 20° C./minute. The energy of melting is a measure of crystallinity in the annealed samples.
  • DSC Differential Scanning Calorimeter
  • FIG. 3 shows sharp decline in crystallinity between 9 and 12 percent meso content.
  • Devolatilized polymer samples from a continuous pilot plant were compounded with dioctyl adipate (a plasticizing agent) and/or silica in a twin screw extruder.
  • the samples were then tested from crystallization rate using the DSC of Example 23.
  • the DSC program included a first upheat, in which the samples were heated from -20° C. to 200° C. at a rate of 20° C./minute, holding at 200° C. for 2 minutes, quenching, and a second upheat from -20° C. to 200° C. at 20° C./minute.
  • the energy of the crystallization exotherm, occurring at a temperature from about 75° C. to about 115° C. is proportional to the amount of crystallization which occurs during this two minute period.
  • the table below shows the increased crystallization observed when the plasticizer dioctyl adipate (DOA) is present, either with or without silica present.
  • DOA plasticizer dioctyl adipate
  • the base polymer, without plasticizer, shows no crystallization during the DSC upheat.
  • the exotherms are reported on a joules per gram of poly(lactide) basis (filler free basis).
  • a devolatilized sample of poly(lactide) polymer was compounded with a variety of potential nucleating agents in a single screw extruder.
  • the candidate nucleating agents were added at a nominal level of 5 percent by weight.
  • the single screw extruder is not as effective of a mixer as would be used commercially, so failure to observe an effect in these tests does not mean that a candidate agent would not be effective if blended more thoroughly.
  • a positive result in this test demonstrates potential ability to increase crystallization rates. Additives which increased crystallinity in the second upheat (on a quenched sample) were rated ++, additives which showed an effect only on the first upheat were rated +, and additives which showed no effect were rated 0.
  • the extent of crystallization was determined by DSC from the melting endotherm of the crystalline domains formed during the annealing, using a ramp rate of 20° C./minute.
  • the biaxially oriented film developed significantly more crystallinity for each time, as shown in the table below.
  • Each of the films was made from lactide mixtures containing an estimated meso-lactide content of about 12 wt %, with about 88 wt % L-lactide.
  • samples from both of the films developed crystallinity which gave a melting endotherm of about 25 J/gm.
  • the biaxially oriented film had been stretched approximately 4 ⁇ in the machine direction and 2 ⁇ in the transverse direction (using a tenter frame), all at about 63°-74° C.
  • poly(lactide) was blended with cellulose acetate (Tenite 110 from Eastman), cellulose acetate propionate (Tenite 375 from Eastman), and cellulose butyrate (Tenite 575 from Eastman) in levels shown in Table 28.
  • the poly(lactide) had a weight average molecular weight of about 200,000, a meso content of about 10.5%, a residual lactide level of about 0.3%, and a moisture content less than about 300 ppm.
  • the weight percentages of poly(lactide) and cellulose derivatives is shown in the following table:
  • the blends were prepared using a melt temperature of 190°-200° C., die pressure of 18-20 bar, and a screw speed of 250 rpm. All materials but one were pelletized, dried and injection molded into a standard ASTM test specimen mold for testing. Composition 3 was not pelletized due to poor strength of the extruded polymer stand. This is evidence of mechanical incompatibility of the cellulose acetate and poly(lactide). The remaining compositions were tested for tensile strength and elongation to break in accord with ASTM D 638-91 and heat distortion temperature according to ASTM D 648-82.
  • Another test performed on each sample was a test for resistance to hot water.
  • a standard tensile bar is placed in a hot water bath at 190° F. for 3 minutes.
  • the sample is removed from the water and placed in a horizontal position with the flat sides facing up and down with one end of the tensile bar held in a clamp.
  • Samples which have softened as a result of the hot water exposure will bend under the force of gravity.
  • the degree of bend is measured using a protractor.
  • the maximum degree of bend is 90° and constitutes a failure. The best result is no bend of the sample.
  • compositions of poly(lactide) blended with CA, CAP and CAB are compatible enough to exhibit good physical properties.
  • Blends of PLA with high loadings of CAP and CAB may increase the flexibility of unblended poly(lactide). Resistance of poly(lactide) to hot water was dramatically increased by addition of CA, CAP or CAB.
  • Poly(lactide) with a weight average MW of 160,000, a meso content of 8 to 12%, and a moisture level of about 200 ppm was extruded into film using the same method as Example 2.
  • the first upheat and quench is to make each of the samples amorphous, the crystallization exotherm is measured during the 90° C. isothermal run, and the second upheat is used to confirm the isothermal exotherm through a direct measurement of the melting endotherm of the crystalline domains formed during the isothermal annealing.
  • Poly(lactide), copolymerized with 0.55 wt % epoxidized linseed oil, from a continuous pilot plant was dried, devolatilized, redried, and compounded with 25 wt % talc (Ultratalc 609, Pfizer) and 25 wt % plasticizer (Citroflex A-4, Morflex). This material was then dried and cast into a 15 mil sheet. Strips of the sheet, approximate 1" ⁇ 4", were loaded into an MTS test instrument using a 1" gap width and stretched to about 4 ⁇ at room temperature. After stretching, the test samples were removed from the MTS and analyzed by a DSC to determine the amount of stress-induced crystallization, using the net melting endotherm. Crystallization exotherms were not observed for these samples, except for the unstretched control.
  • the lactide had a meso-lactide content of about 8-10%.
  • the material was then cast into 15 mil sheet. Squares of the material, approximately 5" ⁇ 5", were stretched using an Iwamoto biaxial stretcher either in a single direction or biaxially. The stretching temperature was 65° C. and the stretching speed was 10 mm/s. The stretched films were tested by DSC to determine the extent of crystallization.
  • Example 23 shows that a non-oriented sample of comparable meso content has a net endotherm of less than 1 J/gm after 15 minutes of annealing at 85° C.
  • Example 31 The talc filled, plasticized, pellets and unoriented films of Example 31 were stored at room temperature for 12 days and 11 days, respectively. They were then retested by DSC to determine if any crystallization had taken place during storage. Significant crystallization had occurred, and the feed pellets showed a melting endotherm of 17.4 J/gm and the film showed a melting endotherm of 18.8 J/gm on an as-tested basis. This corresponds to 35 J/gm and 38 J/gm on a poly(lactide) basis. No crystallization exotherms were observed during the DSC upheat.
  • Example 32 Additional samples of the polymer film used in Example 32 were subjected to uniaxial stretching on the Iwamoto biaxial stretcher.
  • the polymer after melting and quenching, exhibited a Tg with an inflection point of 59° C. when tested by DSC at a scan rate of 20° C./min.
  • the samples were stretched at various temperatures at a rate of 99 mm/sec and tested by DSC to determine the extent of crystallization. Force curves for the stretching operation were also recorded.
  • the table above shows the development of stress induced crystallinity when the polymer was stretched at temperatures up to 20° C. above Tg. At 80° C. less stress induced crystallinity developed, although the sample crystallized readily during subsequent annealing.
  • the samples stretched at 68° C. and 72° C. show pronounced strain hardening at 300-400% elongation during this test.
  • the samples stretched at higher temperatures did not show the same degree of strain hardening.

Abstract

A semi-crystalline film comprised of a lactide polymer. The lactide polymer comprises a plurality of poly(lactide) polymer chains, residual lactide in concentration of less than about 5 percent and water in concentration of less than about 2000 parts-per-million. A process for manufacturing a semi-crystalline film with the lactide polymer composition is also disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
The present application is a continuation-in-part of U.S. patent application Ser. No. 07/955,690, filed Oct. 2, 1992, now allowed.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semi-crystalline film comprising a melt-stable, biodegradable, lactide polymer composition and a process for manufacturing the film from a melt-stable, biodegradable polymer.
2. Description of the Prior Art
The need for polymeric biodegradable films is well established. Films manufactured from blown or cast processes are well known. Typically in a blown film process, a plastic melt passes through a die which extrudes the molten plastic into an annular shape. Typically, the extruded film is extruded in an upward fashion. As the film moves upward, air is blown into the film which expands the film into a tubular shape. The tube is generally closed at some distance above the die, with a pair of nip rolls.
In a cast film process, a sheet is typically extruded from a slit die. The sheet is thereafter pulled through a series of rollers which cool the extruded sheet and may also elongate the length and width of the sheet to a desired dimension and thickness.
The use of films is widespread and well known in the art. The heaviest use of films occurs in the packaging and disposable article industries. Films employed in the packaging industry include films used in food and non-food packaging, merchandise bags and trash bags. In the disposable article industry, the general uses of films occur in the construction of diapers and personal hygiene articles, including tapes.
In light of depleting landfill space and adequate disposal sites, there is a need for biodegradable films. Currently, films comprising polymers such as polyethylene, polypropylene, polyethylene terephthlate, nylon, polystyrene, polyvinyl chloride and polyvinylidene chloride are popular for their superior extrusion and film-making properties. However, these films are not biodegradable. Furthermore, these films are generally noncompostable, which is undesirable from an environmental point of view.
Films have been developed which are generally considered to be biodegradable. These are films which purportedly have adequate properties to permit them to break down when exposed to conditions which lead to composting. Examples of such arguably biodegradable films include those made from polycaprolactone, starch biopolymers and polyvinyl alcohol.
Although films extruded from these materials have been employed in film containing articles, many problems have been encountered with their use. Often the films are not completely biodegradable or compostable. Furthermore, some biodegradable films may also be unduly sensitive to water, either limiting the use of the film or requiring some type of surface treatment to the film, often rendering the film nonbiodegradable. Others have inadequate heat resistance for wide spread use. Thus, there is a need for a film which is completely biodegradable.
The present invention recognizes the importance of crystallinity and further introduces methods to achieve such crystallinity.
The use of lactic acid and lactide to manufacture a biodegradable polymer is known in the medical industry. As disclosed by Nieuwenhuis et al. (U.S. Pat. No. 5,053,485), such polymers have been used for making biodegradable sutures, clamps, bone plates and biologically active controlled release devices. Processes developed for the manufacture of polymers to be utilized in the medical industry have incorporated techniques which respond to the need for high purity and biocompatability in the final product. These processes were designed to produce small volumes of high dollar-value products, with less emphasis on manufacturing cost and yield.
In order to meet projected needs for biodegradable packaging materials, others have endeavored to optimize lactide polymer processing systems. Gruber et al. (U.S. Pat. No. 5,142,023) disclose a continuous process for the manufacture of lactide polymers with controlled optical purity from lactic acid having physical properties suitable for replacing present petrochemical-based polymers.
Generally, manufacturers of polymers utilizing processes such as those disclosed by Gruber et al. will convert raw material monomers into polymer beads, resins or other pelletized or powdered products. The polymer in this form may then be sold to end users who convert, i.e., extrude, blow-mold, cast films, blow films, thermoform, injection-mold or fiber-spin the polymer at elevated temperatures to form useful articles. The above processes are collectively referred to as melt-processing. Polymers produced by processes such as those disclosed by Gruber et al., which are to be sold commercially as beads, resins, powders or other non-finished solid forms are generally referred to collectively as polymer resins.
Prior to the present invention, it is believed that there has been no disclosure of a combination of composition control and melt stability requirements which will lead to the production of commercially viable, semi- crystalline lactide polymer film.
It is generally known that lactide polymers or poly(lactide) are unstable. The concept of instability has both negative and positive aspects. A positive aspect is the biodegradation or other forms of degradation which occur when lactide polymers or articles manufactured from lactide polymers are discarded or composted after completing their useful life. A negative aspect of such instability is the degradation of lactide polymers during processing at elevated temperatures as, for example, during melt-processing by end-user purchasers of polymer resins. Thus, the same properties that make lactide polymers desirable as replacements for non-degradable petrochemical polymers also create undesirable effects during processing which must be overcome.
Lactide polymer degradation at elevated temperature has been the subject of several studies, including: I. C. McNeill and H. A. Leiper, Polymer Degradation and Stability, vol. 11, pp. 267-285 (1985); I. C. McNeill and H. A. Leiper, Polymer Degradation and Stability, vol. 11, pp. 309-326 (1985); M. C. Gupta and V. G. Deshmukh, Colloid & Polymer Science, vol. 260, pp. 308-311 (1982); M. C. Gupta and V. G. Deshmukh, Colloid & Polymer Science, vol. 260, pp. 514-517 (1982); Ingo Luderwald, Dev. Polymer Degradation, vol. 2, pp. 77-98 (1979); Domenico Garozzo, Mario Giuffrida, and Giorgio Montaudo, Macromolecules, vol. 19, pp. 1643-1649 (1986); and, K. Jamshidi, S. H. Hyon and Y. Ikada, Polymer, vol. 29, pp. 2229-2234 (1988).
It is known that lactide polymers exhibit an equilibrium relationship with lactide as represented by the reaction below: ##STR1##
No consensus has been reached as to what the primary degradation pathways are at elevated processing temperatures. One of the proposed reaction pathways includes the reaction of a hydroxyl end group in a "back-biting" reaction to form lactide. This equilibrium reaction is illustrated above. Other proposed reaction pathways include: reaction of the hydroxyl end group in a "back-biting" reaction to form cyclic oligomers, chain scission through hydrolysis of the ester bonds, an intramolecular beta-elimination reaction producing a new acid end group and an unsaturated carbon-carbon bond, and radical chain decomposition reactions. Regardless of the mechanism or mechanisms involved, the fact that substantial degradation occurs at elevated temperatures, such as those used by melt-processors, creates an obstacle to use of lactide polymers as a replacement for petrochemical-based polymers. It is apparent that degradation of the polymer during melt-processing must be reduced to a commercially acceptable rate while the polymer maintains the qualities of biodegradation or compostability which make it so desirable. It is believed this problem has not been addressed prior to the developments disclosed herein.
As indicated above, poly(lactide)s have been produced in the past, but primarily for use in medical devices. These polymers exhibit biodegradability, but also a more stringent requirement of being bioresorbable or biocompatible. As disclosed by M. Vert, Die Ingwandte Makromolekulare Chemie, vol. 166-167, pp. 155-168 (1989), "The use of additives is precluded because they can leach out easily in body fluids and then be recognized as toxic, or, at least, they can be the source of fast aging with loss of the properties which motivated their use. Therefore, it is much more suitable to achieve property adjustment through chemical or physical structure factors, even if aging is still a problem." Thus, work aimed at the bioresorbable or biocompatible market focused on poly(lactide) and blends which did not include any additives.
Other disclosures in the medical area include Nieuwenhuis (European Patent No. 0 314 245), Nieuwenhuis (U.S. Pat. No. 5,053,485), Eitenmuller (U.S. Pat. No. 5,108,399), Shinoda (U.S. Pat. No. 5,041,529), Fouty (Canadian Patent No. 808,731), Fouty (Canadian Patent No. 923,245), Schneider (Canadian Patent No. 863,673), and Nakamura et al., Bio. Materials and Clinical Applications, Vol. 7, p. 759 (1987). As disclosed in these references, in the high value, low volume medical specialty market, poly(lactide) or lactide polymers and copolymers can be given the required physical properties by generating lactide of very high purity by means of such methods as solvent extraction or recrystallization followed by polymerization. The polymer generated from this high purity lactide is a very high molecular weight product which will retain its physical properties even if substantial degradation occurs and the molecular weight drops significantly during processing. Also, the polymer may be precipitated from a solvent in order to remove residual monomer and catalysts. Each of these treatments add stability to the polymer, but clearly at a high cost which would not be feasible for lactide polymer compositions which are to be used to replace inexpensive petrochemical-based polymers in the manufacture of films.
Furthermore, it is well-known that an increase in molecular weight generally results in an increase in a polymer's viscosity. A viscosity which is too high can prevent melt-processing of the polymer due to physical/mechanical limitations of the melt-processing equipment. Melt-processing of higher molecular weight polymers generally requires the use of increased temperatures to sufficiently reduce viscosity so that processing can proceed. However, there is an upper limit to temperatures used during processing. Increased temperatures increase degradation of the lactide polymer, as the previously-cited studies disclose.
Jamshidi et al., Polymer, Vol. 29, pp. 2229-2234 (1988) disclose that the glass transition temperature of a lactide polymer, Tg, plateaus at about 57° C. for poly(lactide) having a number average molecular weight of greater than 10,000. It is also disclosed that the melting point, Tm, of poly (L-lactide) levels off at about 184° C. for semi-crystalline lactide polymers having a number average molecular weight of about 70,000 or higher. This indicates that at a relatively low molecular weight, at least some physical properties of lactide polymers plateau and remain constant. Sinclair et al. (U.S. Pat. No. 5,180,765) disclose the use of residual monomer, lactic acid or lactic acid oligomers to plasticize poly(lactide) polymers, with plasticizer levels of 2-60 percent. Loomis (U.S. Pat. No. 5,076,983) discloses a process for manufacturing a self-supporting film in which the oligomers of hydroxy acids are used as plasticizing agents. Loomis and Sinclair et al. disclose that the use of a plasticizer such as lactide or oligomers of lactic acid is beneficial to produce more flexible materials which are considered to be preferable. Sinclair et al., however, disclose that residual monomer can deposit out on rollers during processing. Loomis also recognizes that excessive levels of lactide or oligomers of lactic acid can cause unevenness in films and may separate and stick to and foul processing equipment. Thus, plasticizing as recommended, negatively impacts melt-processability in certain applications.
Accordingly, a need exists for a lactide polymer which is melt-stable under the elevated temperatures common to melt-processing resins in the manufacture of film. The needed melt-stable polymer composition must also exhibit sufficient compostability or degradability after its useful life as a film. Further, the melt-stable polymer must be processable in existing melt-processing equipment, by exhibiting sufficiently low viscosities at melt-processing temperatures while polymer degradation and lactide formation remains below a point of substantial degradation and does not cause excessive fouling of processing equipment. Furthermore, the lactide polymer must retain its molecular weight, viscosity and other physical properties within commercially-acceptable levels through the film manufacturing process. The present invention also offers further advantages over the prior art and solves other problems associated therewith.
SUMMARY OF THE INVENTION
According to the present invention, a semi-crystalline poly(lactide) film exhibiting a net melting endotherm greater than about 10 joules per gram is provided. The semi-crystalline poly(lactide) film comprises a melt-stable, lactide polymer composition comprising: a plurality of poly(lactide) polymer chains, the polymer being a reaction product of polymerizing a lactide mixture comprising less than about 15 percent by weight meso-lactide. The remaining lactide can be L-lactide, D-lactide or mixtures thereof provided that the overall lactide mixture comprises at least about 85% of either the L or D lactide isomer. This area is shown in FIG. 4. The polymer has residual lactide in a concentration of less than about 2 percent by weight; and water in a concentration of less than about 2,000 parts per million. A process for the manufacture of the film is also provided. For the purposes of the present invention, the film may be manufactured from any number of methods and is not to be limited by the particular method.
Optionally, stabilizing agents in the form of anti-oxidants and water scavengers may be added. Further, plasticizers, nucleating agents, anti-static agents, slip aids and anti-blocking agents may be added. The resultant film is biodegradable and may be disposed of in an environmentally sound fashion.
Poly(lactide) is a polymeric material which offers unique advantages as a film not only in the biodegradable sense, but in the manufacturing process as well.
The present invention describes a method of increasing the degree of crystallinity in a film or sheet by drawing the film in a machine and/or transverse direction orientation at temperatures near the Tg. The Tg can be lowered to near room temperature through the use of plasticizers.
Strain hardening is a phenomenon which, if present, can be used to obtain high quality, uniform, semi-crystalline films. A description of strain hardening in stretching of films of poly( ethylene 2,6, naphthalene dicarboxilate) is given by Cakmak et al. [M. Cakmak, Y. D. Wang, and M. Simhambhatla, Polymer Engineering and Science, June 1990, Vol. 30, p 721-733]. Strain hardening can be identified by an increase in the force required to continue elongation of a film. The essential feature of this phenomenon is the appearance of necks (thin areas) during the stretching operation. High amounts of stretching occurs locally in the necked region, causing it to elongate more than the surrounding areas. The elongation presumably causes the further crystallization of the previous "weak" neck. A neck elsewhere in the film then forms, elongates, crystallizes, hardens and increases its resistance to further elongation. This continues until all areas of the film have once again reached a uniform thickness. As shown by Cakmak et al., the process results in very smooth, high quality films.
We have observed necking in poly(lactide) as it has been subjected to stress induced crystallization, and believe that strain hardening may be occurring. The films which have stretched often feel smoother to the touch, although no surface profiling tests have been done. The films of the present invention may be used in articles such as diapers, packaging film, agricultural mulch film, bags and tape.
The films of the present invention are superior in diaper constructions as compared to other films such as polypropylene or polyethylene. The typical construction of a diaper comprises an outer, water impervious back sheet, a middle absorbent layer and an inner layer. The outer back sheet, comprising the exterior of the diaper, is desirable from an environmental point of view if it is biodegradable. The film of the present invention satisfies this environmental concern by being biodegradable and compostable.
Furthermore, a poly(lactide) film, unlike other biodegradable polymers, is believed to not support microbial growth during storage and typical film use. Starch or other biodegradable polymers, when exposed to warm, damp environments, will promote the growth of unhealthy microbes. This is undesirable in most personal hygiene products. Thus, the present invention has yet another advantage over prior biodegradable polymers.
Another advantage of the present invention is the high surface energy of poly(lactide) films. Poly(lactide) is a material with a relatively high surface energy, when compared to other films. As the surface energy of an extruded film increases, the driving force to remain intact and to minimize surface area increases, therefore the tendency to form a smooth, coherent, high gloss film increases. A high surface energy film also has the advantage of having a surface which is easier to print on. This is an important feature in packaging applications and diapers.
The film of the present invention exhibits a higher surface energy than untreated polyolefin films. In order to produce a satisfactory printing surface, these films must first be modified. This not only increases the costs associated with production of the films, but the modification treatment will diffuse into the film and will produce an unsatisfactory printing surface.
The surface energy of substantially pure poly(lactide) films of the present invention is about 44 dynes/cm. This leads to a surface with satisfactory printing characteristics without surface modification. Slip aids or other additives may reduce the surface energy. Additionally, inks which are typically more difficult to apply onto films, like water based inks, may be applied directly to poly(lactide).
Poly(lactide) is a relatively low viscosity polymer which allows the extrusion of the film to be done at lower temperatures than traditional films. This results in a cost savings to the converter because the extrusion equipment will not require as much power when run at lower temperatures.
Heat sealability is also a property of films which is desirable. Poly(lactide) can be heat sealed at temperatures lower than 70° C., at line pressures lower than 40 psi, and at times less than 2 sec.
It has been found that to improve certain properties for poly(lactide), it may be advantageous to blend a second polymer with poly(lactide). The polymer chosen for blending with poly(lactide) will be one which has the properties necessary for the particular need and is compatible with poly(lactide) to the extent that the particular properties of poly(lactide) are improved. Incompatibility often results in a polymer blend which has inferior properties, such as very low tensile strength and modulus. Properties which may be increased include elongation, heat resistance, rheological properties, degradability, impact resistance, tear resistance and barrier properties to oxygen, moisture, or carbon dioxide.
Polymer Blends
To improve certain properties of poly(lactide), it may be advantageous to blend a second polymer with poly(lactide). The polymer chosen for blending with poly(lactide) will be one which has the properties necessary for the particular need. Incompatibility often results in a polymer blend which has inferior properties, such as very low tensile strength, rheological properties, degradability, and barrier properties to oxygen, moisture or carbon dioxide. Polymers which may be useful for improving the film properties of poly(lactide) include aliphatic polyesters or polyamides made by both ring opening and condensation polymerization, esterified cellulose resins, derivitized starch, polyvinylacetate and any of its partially hydrolyzed products including polyvinylalcohol, polyethers including poly(ethylene oxide), polycarbonates, polyurethanes including those based on aliphatic isocyanates, polyanhydrides, natural rubber and its derivatives including epoxidized natural rubber, block copolymers of styrene and isoprene or butadiene and the hydrogenated version of those polymers, polyacrylates and methacrylates, polyolefins, and polystyrene.
Examples of particular interest include polymers which are also degradable including poly(caprolactone), poly(hydroxybutyrate hydroxyvalerate), cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and poly(vinyl alcohol).
These polymers may be blended with poly(lactide) in percentages of 1 to 95% by weight to make films of improved properties as shown in Example 1.
The above described features and advantages along with various other advantages and features of novelty are pointed out with particularity in the claims of the present application. However, for a better understanding of the invention, its advantages, and objects attained by its use, reference should be made to the drawings which form a further part of the present application and to the accompanying descriptive matter in which there is illustrated and described preferred embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, in which like reference numerals indicate corresponding parts or elements of preferred embodiments of the present invention throughout the several views;
FIG. 1 is a schematic representation of a preferred rocks process for the manufacture of a melt-stable lactide polymer composition; and
FIG. 2 is a graph showing the equilibrium relationship between lactide and poly(lactide) at various temperatures.
FIG. 3 is a graph showing the melting endotherm for annealed samples of poly(lactide).
FIG. 4 is a phase diagram for meso-lactide, L-lactide and D-lactide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
The lactide polymer compositions used in films disclosed herein focus on meeting the requirements of the melt-processor of a lactide polymer resin such as that produced from a process disclosed by Gruber et al. However, the present invention is directed to a poly(lactide) film and is not limited to the lactide polymer composition or process of Gruber et al. Any lactide polymer composition, which comes within the scope of this invention, may be used as a film. As disclosed herein, the problems of degradation, fouling, and lactide formation during melt-processing of lactide polymers are addressed through suggested ranges of molecular weights and compositional limits on impurities such as residual monomer, water and catalyst along with the use of stabilizing agents and catalyst-deactivating agents.
In general, according to the present invention, a melt-stable lactide polymer film and a process for manufacturing a melt-stable lactide polymer film from a melt-stable lactide polymer are disclosed. The use of the term "film" includes not only film, but sheets as well. Lactide polymers are useful due to their recycleable and biodegradable nature. Furthermore, lactide polymers are compostable as illustrated in Example 15 below. Applicants believe the hydrolysis of the ester may be the key to or the first step in degradation of a lactide polymer composition. The mechanism of degradation is not key to the films of the present invention, however it must be recognized that such degradation makes lactide polymers desirable as replacements for presently-utilized non-degradable petrochemical-based polymers used for films.
Applicants have found that the instability of lactide polymers which leads to the beneficial degradation discussed above also creates processing problems. These processing problems include generation of lactide monomer at elevated temperatures and loss in molecular weight believed due to chain scission degradation of the ester bonds and other depolymerization reactions which are not completely understood. No consensus has been reached as to what are the primary degradation pathways at elevated processing temperatures. As previously disclosed, these may include such pathways as equilibrium-driven depolymerization of lactide polymers to form lactide and chain scission through hydrolysis of the ester bonds along with other pathways. For purposes of the present invention, the exact mechanism of degradation at elevated temperatures is not critical.
It is to be understood, however, that degradation of lactide polymers is both beneficial and detrimental. Benefits derive from degradability when articles manufactured from such polymers are discarded. The same or similar types of degradation are detrimental if they occur during processing or prior to the end of the article's useful life.
Lactic acid has two optical isomers, L-lactic acid, also known as (S)-lactic acid, and D-lactic acid, also known as (R)-lactic acid. Three forms of lactide can be derived from the two forms of lactic acid. They are L,L-lactide, also known as L-lactide and which comprises two (S)-lactic acid residuals; D,D-lactide, also known as D-lactide and which comprises two (R)-lactic acid residuals; and meso-lactide, which comprises one each of (R)- and (S)lactic acid residuals. A 50/50 sold mixture of D-lactide and L-lactide with a melting point of about 126° C. is sometimes called D,L-lactide. At temperatures higher than the melting point, it is essentially a liquid mixture of D-lactide and L-lactide.
The similarities and differences between poly(lactic acid) and various poly(lactide)s can best be examined by looking at the distribution of (R) and (S)-lactic acid residuals in the polymers. An L-lactide or D-lactide will introduce a pair of (S) or (R) residuals into the chain, respectively. Meso-lactide introduces an (R,S) or (S,R) dyad. The characteristics of the final polymer will depend for various applications, on the sequencing of the (R) and (S) residuals.
Crystallinity requires relatively long sequences of a particular residual, either long sequences of (R) or of (S). The length of the interrupting sequences may be important for establishing other features of the polymer, such as the rate at which it crystallizes or the melting point of the crystalline phase, or melt processability. The table below shows the expected statistical distribution of the major and minor sequence lengths assuming random polymerization and neglecting transesterification. The table shows data for mixtures containing predominately the (S) configuration, the same results would be obtained for mixtures containing predominately the (R) configuration.
______________________________________                                    
                Probability  Probability                                  
                major sequence                                            
                             minor sequence                               
                having length                                             
                             having length                                
       Optical  at least n = at least n =                                 
Monomer mix                                                               
         Composition                                                      
                    6      10   20   1   2    3                           
______________________________________                                    
Lactic Acid                                                               
95 L/5 D 95 S/5 R   0.77   0.63 0.38 1.0 0.05 0.002                       
90 L/10 D                                                                 
         90 S/10 R  0.59   0.39 0.14 1.0 0.10 0.01                        
Lactide                                                                   
95 L/5 D 95 S/5 R   0.90   0.81 0.63 1.0 1.0  0.05                        
90 L/10 D                                                                 
         90 S/10 R  0.81   0.66 0.39 1.0 1.0  0.10                        
85 L/15 D                                                                 
         85 S/15 R  0.72   0.52 0.23 1.0 1.0  0.15                        
80 L/20 D                                                                 
         80 S/20 R  0.64   0.41 0.13 1.0 1.0  0.20                        
95 L/5 meso                                                               
         97 S/3 R   0.88   0.79 0.61 1.0 0.01 0.00                        
90 L/10 meso                                                              
         95 S/5 R   0.77   0.62 0.37 1.0 0.02 0.00                        
85 L/15 meso                                                              
         92 S/8 R   0.67   0.48 0.21 1.0 0.04 0.00                        
80 L/20 meso                                                              
         90 S/10 R  0.57   0.37 0.12 1.0 0.05 0.00                        
______________________________________                                    
The table above shows, that for the L-lactide system, D-lactide or meso-lactide result in similar major sequence lengths at similar levels. The major sequence length is believed to dominate whether or not crystallization can occur. Fischer et al. [Fischer, E. W., Sterzel, H. J., and Wegner, G., Kolloid-Z. u.Z Polymere 251, p980-990 (1973)] studied the system of L-lactide and D-lactide and reported that crystallization did not occur if the minor component was more than 15% of the polymerization mixture. Our results, documented in Example 24, show that polymers made of L-lactide and meso-lactide will not crystallize when the polymerization mixture contains more than about 15% of the meso-lactide. These results are consistent with the table above, and suggest that a lactide or lactic acid polymer is crystallizable provided that there is at least a 0.5 probability that sequences of the major conformation comprise at least 10 lactic acid residuals.
The table above also shows that polymers of predominately L-lactide with either D-lactide or meso-lactide as minor components have dramatically different sequences of the minor component. For polymers made of L-lactide and meso-lactide there is no chance of having three or more (R)-lactic acid residuals in a row, and a very low probability of having two in a row. For polymers made of L-lactide with low concentrations of D-lactide, the (R)-lactic acid residuals always appear in at least a sequence of length two, with a significant fraction appearing as sequences of length four.
Polymers made either from L- and D-lactic acid (by direct condensation, for example) or from L-lactide with small amounts of meso-lactide have a somewhat similar structure when compared at similar levels of (S) and (R) residuals, as shown in the table above.
Melt-Processing
It is believed that a manufacturer of lactide polymers from a lactide monomer will produce a lactide polymer resin which is in the form of beads or pellets. The melt-processor will convert the resin to a film by elevating the temperature of the resin above at least its glass transition temperature but normally higher and extruding the resin into a film. It is to be understood that the conditions of elevated temperature used in melt-processing cause degradation of lactide polymers during processing. Degradation under melt-processing conditions is shown experimentally in Example 7 based on equilibrium, Example 10 based on catalyst concentration, Example 11 based on catalyst activity, Example 13 based on use of stabilizers and Example 14 based on moisture content. As can be seen in these examples, it is understood that several factors appear to affect the rate of degradation during melt-processing. Applicants have addressed these factors in a combination of compositional requirements and the addition of stabilizing or catalyst-deactivating agents to result in a polymer of lactide which is melt-stable.
In addition, melt-processing frequently produces some proportion of trimmed or rejected material. Environmental concerns and economical efficiencies dictate that this material be reused, typically by regrinding and adding back the material into the polymer feed. This introduces additional thermal stress on the polymer and increases the need for a melt-stable polymer composition.
Melt Stability
The lactide polymers of the present invention are melt-stable. By "melt-stable" it is meant generally that the lactide polymer, when subjected to melt-processing techniques, adequately maintains its physical properties and does not generate by-products in sufficient quantity to foul or coat processing equipment. The melt-stable lactide polymer exhibits reduced degradation and/or reduced lactide formation relative to known lactide polymers. It is to be understood that degradation will occur during melt-processing. The compositional requirements and use of stabilizing agents as disclosed herein reduces the degree of such degradation to a point where physical properties are not significantly affected by melt-processing and fouling by impurities or degradation by-products such as lactide does not occur. Furthermore, the melt-stable polymer should be melt-processable in melt-processing equipment such as that available commercially. Further, the polymer will preferably retain adequate molecular weight and viscosity. The polymer should preferably have sufficiently low viscosity at the temperature of melt-processing so that the extrusion equipment may create an acceptable film. The temperature at which this viscosity is sufficiently low will preferably also be below a temperature at which substantial degradation occurs.
Polymer Composition
The melt-stable lactide polymer film of the present invention comprises a plurality of poly(lactide) polymer chains having a number average molecular weight from about 10,000 to about 300,000. In a preferred composition for a film, the number average molecular weight ranges from about 20,000 to about 275,000. In the most preferred composition, the number average molecular weight ranges from about 40,000 to about 250,000.
In the present invention, a film is considered to be semi-crystalline if it exhibits a net melting endotherm of greater than about 10 J/gm of poly(lactide) when analyzed by a differential scanning calorimeter DSC. To determine whether a film is semi-crystalline it can be tested in a differential scanning calorimeter (DSC), such as marketed by Mettler. An accurately weighed sample of the film, weighing between 5 mg and 15 mg, is placed in the test ampule. A suitable temperature program is to start at -20° C. and scan at 20° C./min to 200° C. Typical features which may be observed include a glass transition at a temperature designated Tg, a relaxation endotherm peak immediately following Tg, a crystallization exotherm peak (generally in the range of 70°-140° C.), and a melting endotherm peak (generally in the range of 100°-200° C.). In the present invention, a film is considered to be semi-crystalline if it exhibits a net melting endotherm of greater than about 10 J/gm of poly(lactide). The net melting endotherm is the energy of the melting endotherm less the energy of the crystallization exotherm if present.
As detailed in Example 9, it appears that the physical properties such as modulus, tensile strength, percentage elongation at break, impact strength, flexural modulus, and flexural strength remain statistically constant when the lactide polymer samples are above a threshold molecular weight. As detailed in Example 22, there is a practical upper limit on molecular weight based on increased viscosity with increased molecular weight. In order to melt-process a high molecular weight lactide polymer, the melt-processing temperature must be increased to reduce the viscosity of the polymer. As pointed out in the Examples, the exact upper limit on molecular weight must be determined for each melt-processing application in that required viscosities vary and residence time within the melt-processing equipment will also vary. Thus, the degree of degradation in each type of processing system will also vary. Based on the disclosure of Example 22, it is believed that one could determine the suitable molecular weight upper limit for meeting the viscosity and degradation requirements in any application.
Lactide polymers can be in either an essentially amorphous form or in a semi-crystalline form. For various applications it will be desirable to have the polymer in semi-crystalline form. Semi-crystalline films have superior heat resistance. The tendency of films to adhere together at temperatures experienced during manufacture, use, shipping or storage when on a roll or part of a product is reduced for semi-crystalline films.
Semi-crystalline films also have decreased permeation to gases, such as oxygen, and moisture. This is an advantage in packaging applications, especially food packaging.
Lactide polymer films with increased crystallinity generally degrade more slowly than amorphous films under conditions of high humidity and heat which results in extended shelf life of the films.
The desired range of compositions for semi-crystalline poly(lactide) is less than about 15 percent by weight meso-lactide and the remaining percent by weight being either L-lactide or D-lactide, wherein at least 85 percent comprises either the L or D-lactide isomer. A more preferred composition contains less than about 12 percent by weight meso-lactide and a most preferred composition has less than about 9 percent by weight meso-lactide with the remainder being substantially all L-lactide and/or D-lactide.
Addition of even small amounts of meso-lactide to the polymerization mixture results in a polymer which is slower to crystallize than polymerization mixtures having lesser amounts of meso-lactide, as detailed in Example 23. Beyond about 15 percent meso content the polymer remains essentially amorphous following the annealing procedure of Example 24.
There are four main methods to increase the rate of crystallization. One is to increase chain mobility at low temperatures, by adding, for example, a plasticizing agent. Dioctyl adipate is an example of a plasticizer which helps crystallization rates in poly(lactide), as detailed in Example 25. A second method to increase the rate of crystallization is to add a nucleating agent, as detailed in Example 26. A third method to induce crystallinity is to orient the polymer molecules. Orientation can be accomplished by drawing during film casting, blowing films, stretching a sheet after it is cast or blown (in multiple directions, if desired), or by the flow of polymer through a small opening in a die. When the process of orientation results in crystallization it is known as stress induced crystallization. This phenomena is illustrated for poly(lactide) in Examples 31 and 32. A fourth method of inducing crystallization is heat-setting, which involves holding a constrained oriented film or fiber at temperatures above Tg. It is demonstrated in Examples 27 and 33. Heat setting involves exposing the film to elevated temperatures, as shown in Plastics Extrusion Technology, F. Hensen (ed), Hanser Publishers, New York, 1988, pp 308, 324. It is preferred to heat set the film under tension to reduce shrinkage during the setting process.
It has been found that poly(lactide) having a meso-content of less than about 12% may be drawn just above its Tg in a machine direction orientation (MDO) or transverse direction orientation (TDO) process to increase the degree of crystallinity. In instances where the Tg of the composition is below room temperature, such as compositions containing at least 15% plasticizer, the sheet may be drawn at room temperature to increase levels of crystallinity from less than 5 J/gm to greater than 15 J/gm. Example 31 demonstrates the increase in crystallinity of a plasticized poly(lactide) sheet upon drawing. The properties of the crystallized and plasticized film are superior with regard to flexible film over non crystallized film. Crystallizing a plasticized film increases the blocking temperature of the film as shown in Example 32. The tensile strength and barrier properties will also increase upon crystallization. Crystallizing lactide polymer films may be performed by drawing the film in either the machine direction or transverse direction or in both directions using draw ratios of 1.1 or greater. The temperature of the draw rolls are generally set at temperatures at or slightly above the Tg of the film. The degree of crystallinity in lactide polymer films containing at least 15% plasticizer may also be increased by storing the film at room temperature until levels of crystallinity greater than 10 J/g is reached. Storing the film under elevated temperatures may increase the rate of crystallization, especially in lactide polymer films containing less than 15% plasticizer.
Crystallization of the lactide polymer may also be done during the manufacture of resin pellets. The crystalline portions of the polymer are melted during film manufacture, therefore recrystallization during film manufacture is still required from semi-crystalline films. However, crystalline resin pellets may be dried at higher temperatures, therefore faster than amorphous resin pellets due to the increased resistance of semi-crystalline resin pellets to adhere together at elevated temperatures. Crystallization of the resin pellets may be done by drawing the strand of polymer to a draw ratio of at least 1.1 as it exits the extruder and prior to being pelletized. Crystallinity may also be increased in lactide polymers containing at least 15% plasticizer by storing the pellets at room temperature for a period of time necessary to increase crystallinity above 10 Joules per gram. Crystalline poly L-lactide exhibits an endotherm of roughly 92 joules per gram at its melting temperature of 170°-190° C., as shown by S. Gogolewski and A. J. Pennings, J. Applied Polymer Science, Vol. 28, pp 1045-1061 (1983). The melting point changes with composition. The degree of crystallinity is roughly proportional to the endotherm on melting. For purposes of the present invention, semi-crystalline poly(lactide) exhibits a net melting endotherm above about 10 joules per gram of poly(lactide). For this invention, an amorphous or non-crystalline poly(lactide) is a poly(lactide) or lactide polymer which exhibits a net melting endotherm of less than about 10 joules per gram of poly(lactide) in the temperature range of about 100°-200° C.
The molecular weight of a polymer sample can be determined through the use of gel permeation chromatography (GPC). In the present case, the GPC analysis was conducted with an Ultrastyragel® column from Waters Chromatography. The mobile phase was chloroform. A refractive index detector with molecular weight calibration using polystyrene standards was used. The GPC temperature was 35° C. Molecular weights were determined by integrating from the highest molecular weight fraction down to 4,000 amu. The region below 4,000 amu is excluded from the calculations of molecular weight in order to improve reproducibility of the number average molecular weight. This material may be separately reported as "oligomers" and residual lactide, as in Example 11.
The residual monomer concentration in the melt-stable lactide polymer composition is less than about 2.0 percent by weight. In a preferred composition, the lactide concentration is less than about 1.0 percent by weight and a most preferred composition has less than about 0.5 percent by weight of lactide. Contrary to disclosures in the art, Applicants have found that the monomer cannot be used as a plasticizing agent in the resin of the present invention due to significant fouling of the extrusion equipment. As detailed in Example 16, it is believed the low levels of monomer concentration do not plasticize the final polymer.
The water concentration within the melt-stable lactide polymer composition is less than about 2,000 parts-per-million. Preferably this concentration is less than 500 parts-per-million and most preferably less than about 100 parts-per-million. As detailed in Example 14, the polymer melt-stability is significantly affected by moisture content. Thus, the melt-stable polymer of the present invention must have the water removed prior to melt-processing. Applicants recognize that water concentration may be reduced prior to processing the polymerized lactide to a resin. Thus, moisture control could be accomplished by packaging such resins in a manner which prevents moisture from contacting the already-dry resin. Alternatively, the moisture content may be reduced at the melt-processor's facility just prior to the melt-processing step in a dryer. Example 14 details the benefit of drying just prior to melt-processing and also details the problems encountered due to water uptake in a polymer resin if not stored in a manner in which moisture exposure is prevented or if not dried prior to melt-processing. As detailed in these examples, Applicants have found that the presence of water causes excessive loss of molecular weight which may affect the physical properties of the melt-processed polymer.
In a preferred composition of the present invention, a stabilizing agent is included in the polymer formulation to reduce degradation of the polymer during production, devolatilization, drying and melt processing by the end user. The stabilizing agents recognized as useful in the present films may include antioxidants and/or water scavengers. Preferred antioxidants are phosphite-containing compounds, hindered phenolic compounds or other phenolic compounds. The antioxidants include such compounds as trialkyl phosphites, mixed alkyl/aryl phosphites, alkylated aryl phosphites, sterically hindered aryl phosphites, aliphatic spirocyclic phosphites, sterically hindered phenyl spirocyclics, sterically hindered bisphosphonites, hydroxyphenyl propionates, hydroxy benzyls, alkylidene bisphenols, alkyl phenols, aromatic amines, thioethers, hindered amines, hydroquinones and mixtures thereof. As detailed in Example 13, many commercially-available stabilizing agents have been tested and fall within the scope of the present melt-stable lactide polymer film. Biodegradable antioxidants are particularly preferred.
The water scavengers which may be utilized in preferred embodiments of the melt-stable lactide polymer film include: carbodiimides, anhydrides, acyl chlorides, isocyanates, alkoxy silanes, and desiccant materials such as clay, alumina, silica gel, zeolites, calcium chloride, calcium carbonate, sodium sulfate, bicarbonates or any other compound which ties up water. Preferably the water scavenger is degradable or compostable. Example 19 details the benefits of utilizing a water scavenger.
In a preferred composition of the present invention, a plasticizer is included in the polymer formulation to improve the film quality of the lactide polymer. More particularly, plasticizers reduce the melt viscosity at a given temperature of poly(lactide), which assists in processing and extruding the polymer at lower temperatures and may improve flexibility and reduce cracking tendencies of the finished film and also improves impact and tear resistance of the film and decreases noise. A plasticizer is useful in concentration levels of about 1 to 40 percent based on weight of polymer. Preferably, a plasticizer is added at a concentration level of about 5 to 25 percent. Most preferably, a plasticizer is added at a concentration level of about 8 to 25 percent.
Selection of a plasticizing agent requires screening of many potential compounds and consideration of several criteria. For use in a biodegradable film the preferred plasticizer is to be biodegradable, non-toxic and compatible with the resin and relatively nonvolatile.
Plasticizers in the general classes of alkyl or aliphatic esters, ether, and multi-functional esters and/or ethers are preferred. These include alkyl phosphate esters, dialkylether diesters, tricarboxylic esters, epoxidized oils and esters, polyesters, polyglycol diesters, alkyl alkylether diesters, aliphatic diesters, alkylether monoesters, citrate esters, dicarboxylic esters, vegetable oils and their derivatives, and esters of glycerine. Most preferred plasticizers are tricarboxylic esters, citrate esters, esters of glycerine and dicarboxylic esters. Citroflex A4® from Morflex is particularly useful. These esters are anticipated to be biodegradable. Plasticizers containing aromatic functionality or halogens are not preferred because of their possible negative impact on the environment.
For example, appropriate non-toxic character is exhibited by triethyl citrate, acetyltriethyl citrate, tri-n-butyl citrate, acetyltri-n-butyl citrate, acetyltri-n-hexyl citrate, n-butyltri-n-hexyl citrate and dioctyl adipate. Appropriate compatibility is exhibited by acetyltri-n-butyl citrate and dioctyl adipate. Other compatible plasticizers include any plasticizers or combination of plasticizers which can be blended with poly(lactide) and are either miscible with poly(lactide) or which form a mechanically stable blend. Corn oil and mineral oil were found to be incompatible when used alone with poly(lactide) because of phase separation (not mechanically stable) and migration of the plasticizer.
Volatility is determined by the vapor pressure of the plasticizer. An appropriate plasticizer must be sufficiently non-volatile such that the plasticizer stays substantially in the resin formulation throughout the process needed to produce the film. Excessive volatility can lead to fouling of process equipment, which is observed when producing films by melt processing poly(lactide) with a high lactide content. Preferred plasticizers should have a vapor pressure of less than about 10 mm Hg at 170° C., more preferred plasticizers should have a vapor pressure of less than 10 mm Hg at 200° C. Lactide, which is not a preferred plasticizer, has a vapor pressure of about 40 mm Hg at 170° C. Example 6 highlights useful plasticizers for the present invention.
Internal plasticizers, which are bonded to the poly(lactide) may also be useful. Epoxides provide one method of introducing an internal plasticizer.
In a preferred composition, nucleating agents may be incorporated during polymerization. Nucleating agents may include selected plasticizers, finely divided minerals, organic compounds, salts of organic acids and imides and finely divided crystalline polymers with a melting point above the processing temperature of poly(lactide). Examples of useful nucleating agents include talc, sodium salt of saccharin, calcium silicate, sodium benzoate, calcium titanate, boron nitride, copper phthalocyanine, isotactic polypropylene, crystalline poly(lactide) and polybutylene terephthalate.
In a preferred composition, fillers may be used to prevent blocking or sticking of layers or rolls of the film during storage and transport. Inorganic fillers include clays and minerals, either surface modified or not. Examples include talc, diatomaceous earth, silica, mica, kaolin, titanium dioxide, perlite, and wollastonite. Preferred inorganic fillers are environmentally stable and non-toxic.
Organic fillers include a variety of forest and agricultural products, either with or without modification. Examples include cellulose, wheat, starch, modified starch, chitin, chitosan, keratin, cellulosic materials derived from agricultural products, gluten, nut shell flour, wood flour, corn cob flour, and guar gum. Preferred organic fillers are derived from renewable sources and are biodegradable. Fillers may be used either alone or as mixtures of two or more fillers. Examples 4 and 5 highlight useful anti-blocking fillers for the present invention. Surface treatments such as corona and flame treatments may also be used to reduce blocking.
Pigments or color agents may also be added as necessary. Examples include titanium dioxide, clays, calcium carbonate, talc, mica, silica, silicates, iron oxides and hydroxides, carbon black and magnesium oxide.
In the manufacture of the melt-stable lactide polymer compositions of the present invention, the reaction to polymerize lactide is catalyzed. Many catalysts have been cited in literature for use in the ring-opening polymerization of lactones. These include but are not limited to: SnCl2, SnBr2, SnCl4, SnBr4, aluminum alkoxides, tin alkoxides, zinc alkoxides, SnO, PbO, Sn (2-ethyl hexanoates), Sb (2-ethyl hexanoates), Bi (2-ethyl hexanoates), Na (2-ethyl hexanoates) (sometimes called octoates), Ca stearates, Mg stearates, Zn stearates, and tetraphenyltin. Applicants have also tested several catalysts for polymerization of lactide at 180° C. which include: tin(II) bis(2-ethyl hexanoate) (commercially available from Atochem, as Fascat 2003, and Air Products as DABCO T-9), dibutyltin diacetate (Fascat 4200®, Atochem), butyltin tris(2-ethyl hexanoate) (Fascat 9102®, Atochem), hydrated monobutyltin oxide (Fascat 9100®, Atochem), antimony triacetate (S-21, Atochem), and antimony tris(ethylene glycoxide) (S-24, Atochem). Of these catalysts, tin(II) bis(2-ethyl hexanoate), butyltin tris(2-ethyl hexanoate) and dibutyltin diacetate appear to be most effective.
Applicants have found the use of catalysts to polymerize lactide significantly affects the stability of the resin product. It appears the catalyst as incorporated into the polymer also is effective at catalyzing the reverse depolymerization reaction. Example 10 details the effect of residual catalyst on degradation. To minimize this negative effect, in a preferred composition, the residual catalyst level in the resin is present in a molar ratio of initial monomer-to-catalyst greater than about 3,000:1, preferably greater than about 5,000:1 and most preferably greater than about 10,000:1. Applicants believe a ratio of about 20,000:1 may be used, but polymerization will be slow. Optimization of catalyst levels and the benefits associated therewith are detailed in Example 20. Applicants have found that when the catalyst level is controlled within these parameters, catalytic activity is sufficient to polymerize the lactide while sufficiently low to enable melt-processing without adverse effect when coupled with low residual monomer level and low water concentration as described above in polymers of molecular weight between 10,000 to about 300,000. It is believed in most applications the addition of a stabilizing agent may be unnecessary if the catalyst level is optimized.
Applicants have also found that catalyst concentration may be reduced subsequent to polymerization by precipitation from a solvent. Example 21 demonstrates potential catalyst removal by precipitation from a solvent. This produces a resin with reduced catalyst concentration. In an alternative embodiment, the catalyst means for catalyzing the polymerization of lactide to form the poly(lactide) polymer chains which was incorporated into the melt-stable lactide polymer composition during polymerization is deactivated by including in the melt-stable lactide polymer composition a catalyst deactivating agent in amounts sufficient to reduce catalytic depolymerization of the poly(lactide) polymer chains. Example 11 details the benefits of utilizing a catalyst deactivating agent. Such catalyst-deactivating agents include hindered, alkyl, aryl and phenolic hydrazides, amides of aliphatic and aromatic mono- and dicarboxylic acids, cyclic amides, hydrazones and bishydrazones of aliphatic and aromatic aldehydes, hydrazides of aliphatic and aromatic mono- and dicarboxylic acids, bis-acylated hydrazine derivatives, and heterocyclic compounds. A preferred metal deactivator is Irganox® MD1024 from Ciba-Geigy. Biodegradable metal deactivators are particularly preferred.
In an alternative embodiment, the catalyst concentration is reduced to near zero by utilizing a solid-supported catalyst to polymerize lactide. The feasibility of utilizing such a catalyst is detailed in Example 8. It is believed catalysts which may be utilized include supported metal catalysts, solid acid catalysts, acid clays, alumina silicates, alumina, silica and mixtures thereof.
In a preferred composition, the catalyst usage and/or deactivation is controlled to reduce depolymerization of the poly(lactide) polymer during melt-processing to less than about 2 percent by weight generation of lactide from a devolatilized sample in the first hour at 180° C. and atmospheric pressure. More preferably, the amount of lactide generated is less than about 1 percent by weight in the first hour and most preferably less than about 0.5 percent by weight in the first hour.
A preferred melt-stable lactide polymer composition is the reaction product of polymerization of lactide at a temperature greater than about 160° C. Applicants have found that polymerization at higher temperatures result in a characteristically different polymer which is believed to have improved melt stability due to increased transesterification during polymerization. The benefits of higher temperature polymerization are detailed in Example 12.
Melt-Stable Lactide Polymer Process
The process for the manufacture of a melt-stable lactide polymer comprises the steps of first providing a lactide mixture wherein the mixture contains less than 15 percent by weight meso-lactide with the remainder being L-lactide and/or D-lactide. Such purified lactide stream may be such as that produced in the process disclosed by Gruber et al., although the source of lactide is not critical to the present invention.
The lactide mixture is polymerized to form a lactide polymer or poly(lactide) with some residual unreacted monomer in the presence of a catalyst means for catalyzing the polymerization of lactide to form poly(lactide). Catalysts suitable for such polymerization have been listed previously. The concentration of catalysts utilized may be optimized as detailed in the following examples and discussed previously.
In a preferred embodiment, a stabilizing agent, which may be an antioxidant and/or a water scavenger is added to the lactide polymer. It is recognized that such stabilizing agents may be added simultaneously with or prior to the polymerization of the lactide to form the lactide polymer. The stabilizing agent may also be added subsequent to polymerization. As previously disclosed, the catalyst usage is adjusted and/or deactivation agent is added in a sufficient amount to reduce depolymerization of poly(lactide) during melt-processing to less than 2 percent by weight generation of lactide from a devolatilized sample in the first hour at 80° C. and atmospheric pressure. More preferably, the stabilizing agent controls lactide generation to less than 1 percent by weight and most preferably less than 0.5 percent by weight in the first hour at 180° C., and atmospheric pressure. Alternatively, the control of catalyst concentration to optimize the balance between necessary catalytic activity to produce poly(lactide) versus the detrimental effects of catalytic depolymerization or degradation of the lactide polymer may be utilized to obviate the need for adding a stabilizing agent.
The lactide polymer is then devolatilized to remove unreacted monomer which may also be a by-product of decomposition reactions or the equilibrium-driven depolymerization of poly(lactide). Any residual water which may be present in the polymer would also be removed during devolatilization, although it is recognized that a separate drying step may be utilized to reduce the water concentration to less than about 2,000 parts-per-million. The devolatilization of the lactide polymer may take place in any known devolatilization process. The key to selection of a process is operation at an elevated temperature and usually under conditions of vacuum to allow separation of the volatile components from the polymer. Such processes include a stirred tank devolatilization or a melt-extrusion process which includes a devolatilization chamber and the like. An inert gas sweep is useful for improved devolatization.
In a preferred process for manufacture of a melt-stable lactide polymer composition, the process also includes the step of adding a molecular weight control agent to the lactide prior to catalyzing the polymerization of the lactide. For example, molecular weight control agents include active hydrogen-bearing compounds, such as lactic acid, esters of lactic acid, alcohols, amines, glycols, diols and triols which function as chain-initiating agents. Such molecular weight control agents are added in sufficient quantity to control the number average molecular weight of the poly(lactide) to between about 10,000 and about 300,000.
Next referring to FIG. 1 which illustrates a preferred process for producing a melt-stable lactide polymer composition. A mixture of lactides enters a mixing vessel (3) through a pipeline (1). A catalyst for polymerizing lactide is also added through a pipeline (13). Within mixing vessel (3) a stabilizing agent may be added through a pipeline (2). A water scavenger may also be added through the pipeline (2). The stabilized lactide mixture is fed through a pipeline (4) to a polymerization process (5). The polymerized lactide or lactide polymer leaves the polymerization process through a pipeline (6). The stream is fed to a second mixing vessel (8) within which a stabilizing agent and/or catalyst deactivating agent may be added through a pipeline (7). The stabilized lactide polymer composition is then fed to a devolatilization process (10) through a pipeline (9). Volatile components leave the devolatilization process through a pipeline (11) and the devolatilized lactide polymer composition leaves the devolatilization process (10) in a pipeline (12). The devolatilized lactide composition is fed to a resin-finishing process (14). Within the resin-finishing process the polymer is solidified and processed to form a pelletized or granular resin or bead. Applicants recognize the polymer may be solidified and processed to form resin or bead first, followed by devolatilization. The resin is then fed to a drying process (16) by conveyance means (15). Within the drying process (16) moisture is removed as a vapor through pipeline (17). The dried lactide polymer resin leaves the drying process (16) by a conveyance means (18) and is fed to a melt-processing apparatus (19). Within the melt-processing apparatus (19) the resin is converted to a useful article as disclosed above. The useful article leaves the melt-processing apparatus (19) through a conveyance means (20).
The following examples further detail advantages of the system disclosed herein:
EXAMPLE 1 Polycaprolactone Blends
Polycaprolactone commercially available as TONE 787 from Union Carbide was added/mixed with poly(lactide) having a number average molecular weight of 157,900, a residual lactide concentration of 0.19%, a meso-lactide concentration of about 10% and a water concentration of less than about 500 ppm on a Leistritz twin screw extruder at 12.8%, 25.6%, 38.4% by weight to poly(lactide). These blends were injection molded into standard ASTM test bars using a Cincinnati Milacron Vista Sentry VST-55 molding press and physical properties were measured and tensiles tested on the bars. The above blends were also extruded into cast film on a Killion extruder with a sheet die, die gap 0.035", with 0.25% by weight Celite Super Floss diatomaceous earth for the purpose of an anti-block agent.
The following table illustrates critical data:
              TABLE 1                                                     
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Compounding: Twin Screw                                                   
                 Cast Film: Killion Conditions                            
______________________________________                                    
conditions                                                                
zone 1: 150° C.                                                    
                 zone 1: 286° F.                                   
zones 2-8: 180° C.                                                 
                 zone 2: 320° F.                                   
zones 9%10: 170° C.                                                
                 zone 3: 320° F.                                   
melt temp: 194° C.                                                 
                 zone 4: 315° F.                                   
die pressure: 44 psi                                                      
                 adaptor: 310° F.                                  
amps: 17.8-20.0  die temp: 310° F.                                 
screw rpm: 300   pressure: 1340 psi                                       
Pressure in      screw rpm: 20.2                                          
devolatization zone                                                       
200 mm hg                                                                 
______________________________________                                    
The following table illustrates the results. It is noted that blends of poly(caprolactone) and poly(lactide are more flexible than unblended poly(lactide) as shown by the increased elongation. This is significant for flexible films as well as other products where decreased brittleness is required.
              TABLE 2                                                     
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                                     Break Mod-                           
                               %     Str.  ulus                           
Film:     Mn:     Mw:     PDI: Lactide                                    
                                     (kpsi)                               
                                           (kpsi)                         
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Sample 1 PLA                                                              
          66662   157866  2.37 0.19  7.9   317                            
Sample 2  68564   170697  2.49 0.33  8.6   350                            
PLA +                                                                     
12.8% tone                                                                
Sample 3  95355   240973  2.53 0.08  N/A   N/A                            
PLA +                                                                     
25.6% tone                                                                
Sample 4  87013   221583  2.55 0.36  N/A   N/A                            
PLA +                                                                     
38.6% tone &                                                              
10% citro.A-4s                                                            
______________________________________                                    
                 Break            Elongation                              
                 Str.    Modulus  at break                                
Injection Molded Test Bars:                                               
                 (kpsi)  (kpsi)   (%)                                     
______________________________________                                    
Sample 6 PLA     7.2     493      5.6 + -1.9                              
Sample 7 12.7% tone + PLA                                                 
                 6.6     403      227 + -52                               
Sample 8 25.6% tone + PLA                                                 
                 3.2     340      250 + -133                              
Sample 9 38.6% tone + PLA                                                 
                 2.7     332      149 + -58                               
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EXAMPLE 2 Example Showing Orientation of Poly(lactide) for Film
To demonstrate the ease and benefit of making oriented poly(lactide) film, an experiment was done to make a sheet using poly(lactide) and orientating that sheet to different degrees. The polymer selected had a 280,000 to 400,000 weight average molecular weight, a 100,000 to 150,000 number average molecular weight, lactide concentration lower than 1%, meso level of about 10 to 20%, and a moisture level lower than about 500 ppm.
The sheet was cast using a 2" diameter single barrier flight screw Davis-Standard extruder with a 24:1 L/D. The die was 24" wide with an adjustable gap. The casting roll was 30" wide and 24" in diameter and equipped with temperature controls. After casting, the sheet was oriented in both the machine (MD) and transverse (TD) directions.
The MD orienter consisted of six 30" wide rolls and five temperature control zones: roll 1 and 2 were for preheat, roll 3 for slow draw, roll 4 for fast draw, roll 5 for heat setting, and roll 6 for cooling the sheet. Draw ratios up to 20 were used for the MD orientation.
The TD was a standard tenter frame with a 3 zone oven. The feed width range for the tenter was 8-48" and the output width range was 16-62". Following the orientation section was a slitter/winder.
Typical conditions used in extruding the sheet are shown below:
 ______________________________________                                    
Extruder  zone 1    350 to 400° F.                                 
                               (177-204° C.)                       
          zone 2    360 to 400° F.                                 
                               (182-204° C.)                       
          zone 3    340 to 350° F.                                 
                               (171-188° C.)                       
Melt pip/adapters                                                         
                330 to 350° F.                                     
                           (166-177° C.)                           
Die zones       330° F.                                            
Head pressure   1640 to 2280 psi                                          
Screw speed     45 to 75 rpm                                              
______________________________________                                    
Melt strength at the die was very good at 330° F. (166° C.). The die was positioned about 0.5 inch off the cast roll, which was run between 112 and 126° F. An air knife was used to pin the melt against the cast roll to reduce neck-in.
Conditions found useful for machine direction orientation of poly(lactide) were temperatures of 65° C. for the preheat rolls, 65° C. and 72° C. for the slow draw roll at low draw ratios and high draw ratios respectively, 65° C. for the fast draw roll, 45° C. for the heat roll, and 20° C. for the cooling roll.
The gap between the slow and fast roll was set to the minimum possible. Orientation took place only slightly above the Tg to give a high degree of molecular alignment. Rolls were collected after MD orientation and some were used for TD orientation. Conditions for transverse direction orientation were 63° C. for the preheat zone, 70° C. for the stretching zone, and 67° C. for the annealing zone. Ambient air was circulated at the oven exit to cool the oriented sheet before winding. The poly(lactide) oriented very well, being easily curved over the rolls and requiring lower process temperatures than standard plastic. The products made were:
______________________________________                                    
       MD       TD     Approx. Thickness                                  
______________________________________                                    
Sample 1 0          0      5 mil                                          
Sample 2 3.2        0      5 mil                                          
Sample 3 3.5        4.3    1 mil                                          
Sample 4 3.5        2.0    2 mil                                          
Sample 5 1.5        2.9    9 mil                                          
Sample 6 1.5        2.0    13 mil                                         
______________________________________                                    
Samples 1, 2 and 3 were tested for tensile and elongation according to ASTM D882 and tear resistance according to ASDTM D689. The results are shown below:
              TABLE 3                                                     
______________________________________                                    
Tensile Strength                                                          
at break         Elongation  Tear Strength                                
(lb/in/mil)      at break (%)                                             
                             (g-cm)                                       
______________________________________                                    
Sample 1                                                                  
       6.9           4.3         40                                       
       7.4           4.8         40                                       
Sample 2                                                                  
       15.8          85.1        16                                       
       6.9           3.2         40                                       
Sample 3                                                                  
       23.9          89.3        32                                       
       10.5          160         128                                      
______________________________________                                    
As the data in the table shows, the tensile strength and flexibility of the poly(lactide) film can be greatly increased by orientation.
EXAMPLE 3 Non-Blocking Characteristics of Plasticized, Crystallized Poly(lactide)
Poly(lactide) having a weight average molecular weight of 165,000, a meso level of about 6%, a lactide level of less than about 0.2%, and a moisture level of less than about 500 ppm was blended with 25% by weight acetyl tributylcitrate (Citroflex A4 from Morflex) in a Werner & Pfleiderer twin screw extruder.
Two films of this composition were prepared in a Carver press equipped with heated platens at a temperature of 300°-350° F. and a dwell time of about 60 seconds. These films were annealed in an oven over four days to induce crystallization of the poly(lactide) samples. The films were tested for resistance to blocking at an elevated temperature. This test was performed by placing two films in contact with each other in an oven held at 60° C. with a 95 gram weight with a surface area of about 2.5 in2 on top of the two films. After more than four hours, the films were removed from the oven and any adhesion between the films was noted. No adhesion occurred during the test. Prior to the annealing and crystallization procedure, films adhered to one another at room temperature.
This result shows that poly(lactide) films containing high levels of plasticizer will have adequate blocking resistance once the poly(lactide) is crystallized.
EXAMPLE 4 Anti-Block Aids
The use of anti-block aids can increase the resistance of two poly(lactide) films to stick together at elevated temperatures. This was demonstrated using poly(lactide) having a weight molecular weight of 165,000, a residual lactide level of about 0.1%, a meso level of about 10%, and a moisture level of about 60 ppm. The anti-block aid was diatomaceous earth having a median particle size of 3.5 microns (Celite Super Floss from Celite) which was dried to a moisture level of about 400 ppm. The diatomaceous earth and poly(lactide) were blended in a twin screw extruder at different levels of anti-block aid and pelletized. The pellets were converted into film using the single screw extruder as in example 2. The films were tested for resistance to adhering to one another by placing two films together with a 92 gram weight on top in an oven set at 60° C. for 2 hours. A failure was when the films could not be separated after being removed from the oven. The results are shown in the table below:
              TABLE 4                                                     
______________________________________                                    
         % Celite                                                         
Sample I.D.                                                               
         Super Floss                                                      
                   Blocking Test 1                                        
                                 Blocking Test 2                          
______________________________________                                    
2113-90-0                                                                 
         0.0       Fused         Fused                                    
2113-90-1                                                                 
         4.1       None          None                                     
2113-90-2                                                                 
         7.9       Some tiny pts. stuck                                   
                                 None                                     
2113-90-3                                                                 
         1.8       Some pts. stuck                                        
                                 None                                     
2113-90-4                                                                 
         0.9       Some pts. stuck                                        
                                 None                                     
2113-90-5                                                                 
         0.45      Some pts. stuck                                        
                                 None                                     
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EXAMPLE 5 Anti-Blocking Agents
Two injection molded disks, 2.5 inch diameter, were placed together with a 94 gram weight on top and held at 50° C. for 24 hours. The disks had the following agents compounded therein. The disks were then cooled to room temperature and pulled apart by hand and ranked for blocking characteristics (considerable, slight and none). The following are the results:
              TABLE 5                                                     
______________________________________                                    
AGENTS                                                                    
______________________________________                                    
Poly(lactide) control considerable                                        
22% wheat gluten      none                                                
10% wheat gluten      slight                                              
22% pecan shell       none                                                
15% pecan shell       slight                                              
23% wollastonite      slight                                              
28% Ultratalc 609     none                                                
23% Ultratalc 609     none                                                
28% Microtuff F talc  slight                                              
22% Microtuff F talc  slight                                              
14% Microtuff F talc  slight                                              
 2% Microtuff F talc  considerable                                        
______________________________________                                    
EXAMPLE 6 Plasticizer Agents
Dried pellets of devolatilized poly(lactide) were processed in a twin screw extruder to allow compounding of various plasticizing agents. The strands leaving the extruder were cooled in a water trough and chopped into pellets. Samples of the pellets were heated at 20° C./minute to 200° C. in a DSC apparatus, held at 200° C. for 2 minutes and rapidly cooled to quench the samples. The quenched samples were then reheated in the DSC apparatus increasing at 20° C./minute to determine the glass transition temperature. These samples were compared to a polymer with no plasticizer. The effect of the plasticizer on the glass transition temperature is shown in the table below. Glass transition temperatures are taken at the mid-point of the transition.
              TABLE 6                                                     
______________________________________                                    
                         Change in T.sub.g /wt.                           
SAMPLE           T.sub.g (C.)                                             
                         percent additive                                 
______________________________________                                    
Control          54.8    --                                               
8% Dioctyl adipate                                                        
                 35.0    2.5                                              
Control + 40% silica                                                      
                 54.5    --                                               
Control + 40% silica +                                                    
                 36.0    3.7                                              
5% dioctyl adipate                                                        
Control          54.6    --                                               
6% Citroflex A-4*                                                         
                 42.6    2.0                                              
12% Citroflex A-4                                                         
                 31.4    1.9                                              
Control          59.3    --                                               
1.6% Citroflex A-4                                                        
                 56.3    1.9                                              
2.9% Citroflex A-4                                                        
                 53.1    2.1                                              
Control          58.4    --                                               
2.1% Citroflex A-4                                                        
                 56.1    1.1                                              
3.4% Citroflex A-4                                                        
                 50.5    2.3                                              
Control          61.6    --                                               
18.6% Citroflex A-2                                                       
                 54.7    0.4                                              
13.1% Citroflex B-6                                                       
                 52.4    0.7                                              
12.6% Citroflex A-6                                                       
                 53.8    0.6                                              
______________________________________                                    
*Citroflex is a registered trademark of Morflex, Inc., Greensboro, N.C. A-4 is the designation of a purified acetyltri-n-butyl citrate. A-2 is the designation of acetyltriethyl citrate, A-6 is the designation of acetyltri-n-hexyl citrate, and B-6 is the designation of n-butyryltri-n-hexyl citrate.
These results show the effectiveness of these plasticizers in reducing the glass transition temperature of poly(lactide). The procedure above was tried using corn oil as a plasticizer. Visual observation showed the corn oil to be not compatible, forming a film on the surface. Corn oil and mineral oil were both not effective as a primary plasticizer with poly(lactide). They may still be useful as a secondary plasticizer, in combination with a compatible primary plasticizer.
EXAMPLE 7 Lactide and Poly(lactide) Equilibrium Concentrations
Experiments were conducted to determine the equilibrium concentration of lactide and poly(lactide) at different temperatures. In these experiments a sample of lactide was polymerized in the presence of a catalyst (tin (II) bis(2-ethyl hexanoate)) and held at a fixed temperature for 18 hours or greater. Beyond this time the residual monomer concentration is believed essentially constant. The content of residual monomer was determined by GPC analysis. GPC analysis was conducted with an Ultrastyragel® column from Waters Chromatography. The mobile phase was chloroform. A refractive index detector with molecular weight calibration using polystyrene standards was used. The GPC temperature was 35° C. Data analysis was completed using the software package Baseline, model 810, version 3.31.
The results of tests conducted on several samples at various temperatures are summarized in the graph of FIG. 2 as indicated by X's on such graph. Also plotted on the graph of FIG. 2 are data points cited in A. Duda and S. Penczek, Macromolecules, vol. 23, pp. 1636-1639 (1990) as indicated by circles on the graph. As can be seen from the graph of FIG. 2, the equilibrium concentration, and thus the driving force behind the depolymerization of poly(lactide) to form lactide, increases dramatically with increased temperature. Thus, melt-processing at elevated temperatures results in degradation of the lactide polymer to form lactide on the basis of equilibrium alone. For example, lactide concentrations below about 2 percent cannot be directly obtained at temperatures of 140° C. or above due to the identified equilibrium relationship between lactide and poly(lactide).
EXAMPLE 8 Lactide Polymerization in the Presence of a Solid Supported Catalyst
Tin (II) Oxide
24 grams of L-lactide (melting point about 97° C.) and 6 grams of D,L-lactide (for the purposes of this invention, D,L-lactide has a melting point of about 126° C.) were combined in a round bottom flask with 0.033 grams of Tin (II) oxide, as a fine powder. This corresponds to the catalyst level of 852:1, molar ratio lactide to tin. The flask was then purged with dry nitrogen 5 times. This was lowered into an oil bath at 160° C. with magnetic stirring. Polymerization time was 8 hours.
Amberlyst 36
24 grams of L-lactide and 6 grams of D,L-lactide were combined in a round bottom flask with 1.06 grams of Amberlyst 36 resin beads. The flask was purged 5 times with dry nitrogen. The flask was lowered into an oil bath at 140° C. with magnetic stirring. Polymerization time was 8 hours. The resin had a stated proton content of 1 meq/gram dry weight resin. The resin was prepared by rinsing 2 times with 10 volumes dry methanol, then dried for several hours under high vacuum for several hours at 40° C.
The polymerization results are shown below:
              TABLE 7                                                     
______________________________________                                    
Sample    Mn       Mw       PDI   % Conversion                            
______________________________________                                    
Tin (II) Oxide                                                            
          77,228   103,161  1.34  54.0                                    
Amberlyst  1,112    1,498   1.34  73.5                                    
______________________________________                                    
EXAMPLE 9 Molecular Weight Relationship to Physical Properties of Lactide Polymers
Poly(lactide) samples with various molecular weights and optical compositions were prepared by polymerizing blends of L-lactide and meso-lactide at 180° C. under nitrogen in a 1-gallon sealed reactor. Tin(II) bis(2-ethyl hexanoate) catalyst was added at a monomer-to-catalyst ratio of 10,000:1. After about 1 hour the molten polymer was drained from the reactor using nitrogen pressure. The sample was poured into a pan and placed in a vacuum oven at about 160° C. for about 4 hours to bring the reaction to near equilibrium levels.
Portions of the samples were then dried under vacuum and processed in an injection molding apparatus (New Britain 75 from New Britain Machine Co.) to produce standard test bars for physical property testing. The results of physical property testing are shown in the following Table 8. The physical property tests were made according to ASTM methods D 638, D 256, and D 790. The reported results are the averages of several tests.
Samples of the test bars after injection molding were analyzed by GPC for molecular weight. Other portions of the test bars were reground and tested in a capillary viscometer to determine the melt-viscosity. These results are also included in Table 8.
Statistical analysis of the data revealed no correlations which were statistically significant between either optical composition or molecular weight and the mechanical properties of modulus, tensile strength, percentage elongation at break, notched Izod impact strength, flexural modulus, or flexural strength. The independence of these properties on molecular weight indicates that all of these samples were above a "threshold" molecular weight required to achieve the intrinsic properties of the polymer in a preferred composition.
The viscosity data show significant correlations with molecular weight. This dependence documents the practical limitation and necessity of controlling polymer molecular weight below an upper limit at which it is impractical to melt-process the polymer. At high molecular weight, high viscosity prevents processing by standard melt-processing equipment. Increases in temperature to reduce viscosity dramatically increase polymer degradation and lactide formation which is also unacceptable.
              TABLE 8                                                     
______________________________________                                    
Meso       Molecular  Viscosity at 173° C. (Pa · S)       
      Lactide  Weight After                                               
                          Final Shear   Shear                             
Sample                                                                    
      In Blend,                                                           
               Injection  IV    Rate    Rate                              
I.D.  Wt %     Weight     (dl/g)                                          
                                100 S.sup.-1                              
                                        1000 S.sup.-1                     
______________________________________                                    
6     40       41000      0.86  5.5     2.9                               
5     10       54000      0.88  10.4    7.2                               
4     20       59000      0.91  10.4    7.2                               
8     10       64000      1.02  15.7    10.0                              
9     40       68000      0.97  12.6    8.1                               
7     20       71000      1.16  36.0    12.9                              
10    20       83000      1.19  35.8    15.8                              
______________________________________                                    
Mechanical Properties of Injection Molded Samples                         
                       %                                                  
              Tensile  Elon- IZOD                                         
      Mod-    Strength gation                                             
                             Impact                                       
                                   Flexural                               
                                          Flexural                        
Sample                                                                    
      ulus    (Yld)    at    ft · lb./                           
                                   Modulus                                
                                          Strength                        
I.D.  MPSI    PSI      Break in    MPSI   PSI                             
______________________________________                                    
6     0.55    6600     3.3   0.39  0.53   11300                           
5     0.56    7800     3.5   0.46  0.54   12500                           
4     0.56    7600     3.9   0.32  0.53   12500                           
8     0.55    7700     3.4   0.47  0.53   12400                           
9     0.59    6700     3.1   0.42  0.52   10600                           
7     0.56    7400     3.3   0.45  0.51   12400                           
10    0.55    6700     3.0   0.47  0.52    9900                           
______________________________________                                    
EXAMPLE 10 Effect of Residual Catalyst on Polymer Degradation
Polymer samples were prepared at four levels of catalyst, corresponding to monomer to catalyst molar ratios of 5,000:1, 10,000:1, 20,000:1, and 40,000:1. The catalyst utilized was tin (II) bis(2-ethyl hexanoate). These samples were then subjected to heating in a TGA apparatus (TA Instruments, Inc., model 951 thermogravometric analyzer with a DuPont 9900 computer support system) with a nitrogen purge. Isothermal conditions of 200° C. for 20 minutes were used. The samples were then analyzed by GPC with a viscosity-based detector and a universal calibration curve to determine the extent of breakdown in molecular weight. The GPC apparatus for this test was a Viscotek Model 200 GPC and a Phenomenex column. The TGA analysis typically resulted in about a 5 percent loss in weight and molecular weight drops of 0 to 70 percent.
The number average molecular weights were converted to a milliequivalent per kilogram basis (1,000,000/Mn) in order to calculate a rate of chain scission events. The results below represent averages of 2-4 replicates on each of the four samples.
              TABLE 9                                                     
______________________________________                                    
Catalyst level  Scission Rate                                             
(monomer/catalyst)                                                        
                (meq/kg*min)                                              
______________________________________                                    
 5,000          1.33                                                      
10,000          0.62                                                      
20,000          0.44                                                      
40,000          0.12                                                      
______________________________________                                    
The rate of chain scission was directly proportional to the residual catalyst level, demonstrating the detrimental effect of catalyst activity on melt-stability under conditions similar to melt-processing. This instability, however, is distinguished from the instability due to the equilibrium relationship between lactide and poly(lactide) detailed in Example 7, in that loss of molecular weight due to catalytic depolymerization by chain scission is evident.
EXAMPLE 11 Catalyst Deactivation Experiment
Two runs were made in a laboratory Parr reactor. Lactide feed was 80 percent L-lactide and 20 percent D,L-lactide. Molecular weight was controlled by adding a small quantity of lactic acid, the target molecular weight was 80,000 Mn.
Lactide was charged to the reactor as a dry mix, the reactor was purged 5 times with nitrogen, and heated up to 180° C. At this point catalyst (5000:1 initial monomer to catalyst molar ratio, Fascat®2003) was charged through a port in the top of the reactor. The reaction was allowed to proceed for 70 minutes at 180° C., with mechanical agitation. Conversion at this point was 93-94 percent, close to the equilibrium value at 180° C. of 96 percent poly(lactide) from FIG. 2. This point is considered t-zero, designating the completion of the polymerization reaction and the beginning of the mixing time. In the control experiment, a sample was taken and the mixture was held at temperature with continued agitation. Samples were taken periodically through a port in the reactor bottom. After 4 hours the reactor was drained. In the example experiment, a sample was taken and 0.25 weight percent of a metal deactivator (Irganox® MD 1024®) was added through the catalyst addition port. The mixture was held at temperature with continued agitation and samples were withdrawn periodically. The reactor was drained after 4 hours. GPC analysis (utilizing the method of Example 7) for these samples was divided into three parts: polymer with molecular weight over 4,000 (for which the Mn and Mw numbers are reported), the percent oligomers (comprising the region with molecular weight greater than lactide but less than 4,000, as distinguished from oligomers as defined by Loomis to include only oligomers up to a molecular weight of 450), and percent lactide (residual monomer). The structure of the oligomers was not certain, but it is believed they were primarily cyclic structures. It is also believed that the metal deactivator, if unreacted, will elute with the oligomer fraction. Quantification of the oligomer fraction is difficult, because the GPC trace is near the baseline in this region.
The analysis of the polymer samples as withdrawn from the reactor at various time intervals for the control and experimental compositions are shown below in Table 10.
              TABLE 10                                                    
______________________________________                                    
                   %         %      %                                     
Mn         Mw      Polymer   Oligomer                                     
                                    Monomer                               
______________________________________                                    
Control                                                                   
t-zero 67,100  119,500 94      0      6.0                                 
0.5 hr 62,500  119,000 95      0.7    3.9                                 
1.0 hr 61,500  116,100 96      0      3.6                                 
1.5 hr 56,000  111,600 95      1.5    3.3                                 
2.0 hr 57,600  110,900 96      0.9    3.1                                 
4.0 hr 51,400  105,400 94      3.3    3.1                                 
Test                                                                      
t-zero 63,200  110,700 93      3.5    3.8                                 
0.5 hr 52,100  108,600 92      4.6    2.9                                 
1.0 hr 52,700  109,200 92      4.9    2.8                                 
1.5 hr 53,400  107,200 93      4.0    3.1                                 
2.0 hr 59,700  111,100 94      0.6    5.8                                 
4.0 hr 51,200  107,300 91      6.1    3.3                                 
______________________________________                                    
The samples were then ground and placed in a 120° C. oven under vacuum (pressure 0.1 inch Hg) for 14 hours. Sample analyses after this treatment are shown below in Table 11.
              TABLE 11                                                    
______________________________________                                    
                    %        %      %                                     
Mn         Mw       Polymer  Oligomer                                     
                                    Monomer                               
______________________________________                                    
Control                                                                   
t-zero 45,500  88,500   98     2.2    0.0                                 
0.5 hr 45,000  88,700   98     2.0    0.0                                 
1.0 hr 43,900  87,200   98     2.0    0.0                                 
1.5 hr 42,600  84,000   98     2.2    0.0                                 
2.0 hr 42,000  85,200   97     3.2    0.0                                 
4.0 hr 41,900  82,800   98     2.0    0.0                                 
Test                                                                      
t-zero 39,300  76,700   96     4.0    0.0                                 
0.5 hr 43,900  85,100   98     2.4    0.0                                 
1.0 hr 55,300  98,600   96     3.8    0.0                                 
1.5 hr 48,400  96,200   95     4.5    0.0                                 
2.0 hr 48,900  101,900  95     5.0    0.0                                 
4.0    50,600  101,900  94     5.6    0.0                                 
______________________________________                                    
In all cases the polymer was completely devolatilized (0.0 percent residual lactide monomer). The data also clearly show that the metal deactivator reduced the degradation of polymer during the devolatilization step (as indicated by the greater loss in Mn for the control samples from Table 9 to Table 10 versus the Test samples). One hour of mixing appears to be long enough to develop most of the benefit.
The samples were stored at room temperature under nitrogen for about 1 week and reanalyzed, as shown below in Table 12.
              TABLE 12                                                    
______________________________________                                    
                    %        %      %                                     
Mn         Mw       Polymer  Oligomer                                     
                                    Monomer                               
______________________________________                                    
Control                                                                   
t-zero 33,500  71,000   100    0.1    0.0                                 
0.5 hr 43,400  95,800   99     1.0    0.0                                 
1.0 hr 44,900  96,300   100    0.1    0.0                                 
1.5 hr 45,900  95,000   100    0.0    0.0                                 
2.0 hr 45,900  94,100   100    0.2    0.0                                 
4.0 hr 43,100  90,100   99     1.3    0.0                                 
Test                                                                      
t-zero 44,600  84,900   100    0.0    0.0                                 
0.5 hr 45,300  90,600   99     1.2    0.0                                 
1.0 hr 47,800  100,000  98     2.4    0.0                                 
1.5 hr 46,600  98,900   96     3.5    0.0                                 
4.0    57,700  110,200  96     4.0    0.3                                 
______________________________________                                    
Equilibrium lactide levels are estimated to be less than 0.2 weight percent at room temperature. Consistent with that, essentially no lactide was observed in any of the samples (detection limit about 0.1 weight percent). The oligomer content in the non-stabilized samples declined and some increase in molecular weight was noted, perhaps due to reincorporation of the (cyclic) oligomers into the polymer. The oligomer depletion reaction was inhibited in the stabilized polymers, with the extent of inhibition dependent on the length of time that the additive was mixed.
The samples were then reheated to 180° C. in sealed vials and held for one hour as a simulation of melt-processing. Analysis of the samples after the heat treatment is given below in Table 13.
              TABLE 13                                                    
______________________________________                                    
                   %         %      %                                     
Mn         Mw      Polymer   Oligomer                                     
                                    Monomer                               
______________________________________                                    
Control                                                                   
t-zero 23,900  60,000  88      8.4    4.0                                 
0.5 hr 23,900  59,600  90      7.7    2.7                                 
1.0 hr 23,700  58,800  88      9.3    2.7                                 
1.5 hr 24,700  58,000  86      10.0   3.8                                 
2.0 hr 26,100  56,400  90      6.8    2.7                                 
4.0 hr 24,800  58,700  92      6.6    1.9                                 
Test                                                                      
t-zero 33,900  64,300  95      2.2    3.1                                 
0.5 hr 17,900  34,600  94      4.8    1.7                                 
1.0 hr 21,200  42,900  94      4.6    1.8                                 
1.5 hr 29,200  56,900  98      0.5    1.8                                 
2.0 hr missing                                                            
4.0 hr 35,700  71,400  95      3.7    1.7                                 
______________________________________                                    
The data for molecular weight show that if the metal deactivator is not mixed into the system long enough then it can have a detrimental impact on stability in the melt. The samples for which the mixing was at least 1.5 hours show no detrimental effect, and the 4 hour sample appears to be somewhat more stable than any of the others based on molecular weight alone. More importantly, the metal deactivator samples show significantly less lactide reformation than the control samples. This effect is gained even in the samples which were mixed for only 0.5 hour. The metals deactivated samples averaged only 1.8 percent lactide after one hour at 180° C., compared to an average of 3.0 percent lactide for the controls. The equilibrium level at 180° C. is about 3.6 percent from FIG. 2. Thus, the use of metal deactivators can reduce the troublesome reformation of lactide during melt-processing of the finished polymer.
EXAMPLE 12 Effect of Increased Polymerization Temperature on Polymer Characteristics
L-lactide (Boeringer Ingleheim, S-grade) was used as received, meso-lactide (PURAC) was purified by distillation to remove traces of D- and L-lactide. The melting point of the purified meso-lactide was 54° C. Lactide mixtures were made up to the following ratios: 100 percent L-lactide, 90/10 L-lactide/meso-lactide, 70/30 L-lactide/meso-lactide, 50/50 L-lactide/meso-lactide, and 100 percent meso-lactide. Catalyst level was 2,500:1 molar ratio of initial monomer to tin with the tin being tin(II) bis (2-ethyl hexanoate) (Fascat® 9002). Lactic acid was added as a molecular weight control agent to target a number average molecular weight of 50,000 (the same amount was added to all samples). Polymerization times were estimated to obtain conversions of 50 percent and 90 percent. For 120° C. this was 4 hours and 16 hours, respectively. For 180° C. these times were 10 minutes and 50 minutes, respectively. Below in Table 14 are the GPC results (method of Example 7) of tests on the polymer samples produced by this procedure.
              TABLE 14                                                    
______________________________________                                    
L/meso  Temp     Mn      Mw      PDI   % Conv                             
______________________________________                                    
100% L  120° C.                                                    
                 31,014  33,774  1.09  53.2                               
                 45,864  52,574  1.15  87.1                               
100% L  180° C.                                                    
                 27,785  32,432  1.17  46.7                               
                 56,839  98,125  1.73  93.3                               
90/10   120° C.                                                    
                 34,541  38,586  1.12  62.3                               
                 29,222  34,466  1.18  89.3                               
90/10   180° C.                                                    
                 31,632  35,713  1.13  48.5                               
                 57,925  110,841 1.91  94.8                               
70/30   120° C.                                                    
                 41,211  45,222  1.10  60.1                               
                 58,284  71,257  1.22  89.1                               
70/30   180° C.                                                    
                 32,292  37,401  1.16  53.8                               
                 51,245  107,698 2.10  96.5                               
50/50   120° C.                                                    
                 15,888  17,969  1.13  57.8                               
                 25,539  31,834  1.25  90.6                               
50/50   180° C.                                                    
                 34,375  42,018  1.22  62.5                               
                 44,590  98,028  2.20  95.5                               
100% meso                                                                 
        120° C.                                                    
                 33,571  40,635  1.21  73.4                               
                 45,237  68,142  1.51  94.3                               
100% meso                                                                 
        180° C.                                                    
                 30,976  42,987  1.39  67.6                               
                 40,038  83,815  2.09  96.6                               
______________________________________                                    
The results show that the ultimate number average molecular weight was not significantly affected by the temperature of polymerization, with an average of 41,000 at 120° C. and 50,000 at 180° C. This implies that each lactic acid molecule initiates about one polymer chain, regardless of temperature. The ultimate weight average molecular weight is, however, significantly affected by temperature. At 120° C. the weight average molecular weight averaged 52,000 and at 180° C. the average was 100,000. This is believed to be due to a relative increase in the rate of transesterification at 180° C. The polydispersity index (PDI) at high conversion also reflects this, averaging 1.3 at 120° C. and 2.0 at 180° C. It is believed these differences would have a significant effect on the melt-processing characteristics of the polymer, with the higher weight average molecular weight of the polymer produced at 180° C. expected to translate into better melt strength and processability.
These experiments show that polymerization at a higher temperature results in a polymer that is characteristically different. Further, the glass transition temperature for the samples polymerized at higher temperature is higher.
EXAMPLE 13 Experiments with Stabilizing Agents and Metal Deactivators
Test 1
Conditions: vial polymerization, (Lactide is melted under a nitrogen-purged atmosphere in a round bottom flask with stirring. Catalyst and additives are added and aliquots of the mixtures are pipetted into silanized glass vials. Typically 5-10 grams of reaction mixture are used in a 16 ml. vial. The vials are tightly capped and placed into a preheated oil bath.) 10,000:1 molar ratio of lactide-to-tin, tin(II) bis(2-ethyl hexanoate) catalyst, 0.2 wt percent Ultranox®626 in tetrahydrofuran (THF). 180° C. Time was 90 minutes.
The control with tin only polymerized to 84 percent conversion and reached a MWn of 31,700. The example with tin and Ultranox® polymerized to 83 percent conversion and reached a number average molecular weight (MWn) of 39,800; an increase of 26 percent over the control.
The control sample turned light yellow, the sample with stabilizer remained colorless.
Test 2
Conditions: vial polymerization, 5000:1 molar ratio of lactide to tin, tin(II) bis(2-ethyl hexanoate) catalyst, 0.25 wt percent Ultranox®626 (in THF). 180° C. Time was 60 minutes. Lactide was used from the above described Gruber et al. process.
The control with tin alone polymerized to 67 percent conversion and reached a MWn of 62,900. The example with tin and Ultranox® polymerized to 66 percent conversion and reached a MWn of 75800; an increase of 21 percent over the control.
A second example with tin(II) bis(2-ethyl hexanoate), Ultranox®, and 0.50 percent of Irganox®1076, which is a phenolic antioxidant, polymerized to 66 percent conversion and reached a number average molecular weight (MWn) of 74500; an increase of 18 percent over the control.
All samples were a dark yellow color, although the samples with stabilizer had a slightly lower absorbance at 300 rim.
Test 3
Conditions: vial polymerization, 10,000:1 molar ratio of lactide to tin, tin(II) bis(2-ethyl hexanoate) catalyst, 180° C., 80 percent L-lactide and 20 percent D,L-lactide purchased from Henley and Aldrich, respectively. Lactic acid was added to control molecular weight to about 75,000 at full conversion. One sample included 0.25 percent Ultranox® 626 phosphite stabilizer, one included 0.25 percent Irganox® 1076 antioxidant, and one control sample.
Samples were taken at various times and analyzed by GPC for conversion and molecular weight (the method of Example 7). The results are summarized in Table 9 below.
              TABLE 15                                                    
______________________________________                                    
Time Control      Irganox ®                                           
                               Ultranox ®                             
(hrs)                                                                     
     Mn      % conv   Mn    % conv Mn     % conv                          
______________________________________                                    
1    31,000  46       35,900                                              
                            41     66,500 61                              
2    45,400  74       56,800                                              
                            74     102,700                                
                                          83                              
4    69,600  93       74,100                                              
                            93     97,200 91                              
11   52,900  95       60,700                                              
                            95     71,500 94                              
______________________________________                                    
The sample with phosphite stabilizer polymerized faster, shown by the higher conversion at 1 and 2 hours, and went to a higher molecular weight than the control or the sample with Irganox®. The phosphite stabilized sample had a molecular weight more than 30 percent higher than the control for all time periods.
Test 4
The experiment above was repeated to compare the control to the phosphite-stabilized polymer, as summarized in Table 16 below.
              TABLE 16                                                    
______________________________________                                    
Time    Control             Ultranox ®                                
(hrs)   Mn      % conv      Mn     % conv                                 
______________________________________                                    
1       36,600  37          71,500 59                                     
2       51,700  70          95,200 85                                     
4       64,400  91          103,700                                       
                                   94                                     
8       58,100  96          95,700 94                                     
______________________________________                                    
The sample with phosphite stabilizer again polymerized faster and went to a higher molecular weight than the non-stabilized sample. The phosphite stabilized sample had a molecular weight more than 60% higher than the control for all time periods.
Test 5
Conditions: vial polymerization, 5,000:1 molar ratio of lactide to tin, tin(II) bis(2-ethyl hexanoate) catalyst, 180° C., 80 percent L-lactide and 20 percent D,L-lactide purchased from Henley and Aldrich. Lactic acid was added to control number average molecular weight to an estimated 80,000 at full conversion. One sample was run with 0.25 percent Ultranox® 626 phosphite stabilizer, one with 0.25 percent Irganox® 1076 antioxidant, and one control sample. Samples taken at various times and analyzed by GPC (the method of Example 1) for conversion and molecular weight. The results are tabulated in Table 17 below.
              TABLE 17                                                    
______________________________________                                    
Time Control      Irganox ®                                           
                               Ultranox ®                             
(hrs)                                                                     
     Mn      % conv   Mn    % conv Mn     % conv                          
______________________________________                                    
1    83,600  76       121,900                                             
                            83     162,300                                
                                          87                              
4    74,400  93       104,300                                             
                            95     123,900                                
                                          96                              
24   40,200  96        52,000                                             
                            96     96,900 97                              
48   34,200  97        30,400                                             
                            96     56,500 96                              
72   25,000  96        22,400                                             
                            96     69,500 96                              
______________________________________                                    
The phosphite-stabilized sample had a molecular weight more than 60 percent higher than the control for all time periods. After 72 hours it had a molecular weight 2.8 times higher than the control. The sample with antioxidant showed an initial increase in molecular weight, relative to the control, but the effect disappeared after 48 hours. The phosphite stabilized sample was significantly lighter in color than the control or the antioxidant treated sample.
Test 6
Conditions: vial polymerization, 5000:1 molar ratio of lactide to tin, tin(II) bis(2-ethyl hexanoate) catalyst, 0.25 wt percent Ultranox®626 (in THF). 180° C. Time was two hours. Gruber et al. process lactide washed with isopropyl alcohol was used. The control with tin alone polymerized to 95 percent conversion and reached a number average molecular weight of 118,000. The example with tin and Ultranox® polymerized to percent conversion and reached a number average molecular weight of 151,000, an increase of 28 percent over the control.
Test 7
Conditions: vial polymerization at 180° C. 5000:1 molar ratio of lactide to tin, tin(II) bis(2-ethyl hexanoate) catalyst. Lactide was 80percent L-lactide and 20 percent D,L-lactide, purchased from Henley and from Aldrich. Lactic acid was added to target the molecular weight to an Mn of 80,000. All stabilizers were added at 0.25 weight percent. Molecular weight (number average) was determined for samples pulled at 3 hours, while rate constants were based on samples pulled at 1 hour. The results of these screening tests on many stabilizing agents following the above procedure are detailed below in Table 18. Product designations in Table 18 are tradenames or registered trademarks.
              TABLE 18                                                    
______________________________________                                    
                           % Con-   Relative                              
Sample            MWn      version  Rate                                  
______________________________________                                    
Control 1             65,000   95.9   90                                  
Control 2             85,000   95.9   100                                 
Control 3             76,000   96.6   100                                 
Control 4             69,000   96.2   100                                 
Control 5             74,000   96.8   110                                 
Control 6             70,000   97.2   110                                 
PHOSPHITES                                                                
Ultranox 626                                                              
           (GE)       103,000  96.8   100                                 
Weston TDP (GE)       64,000   70.0   60                                  
Weston PDDP                                                               
           (GE)       67,000   76.7   60                                  
Weston PNPG                                                               
           (GE)       92,000   94.1   100                                 
Irgafos 168                                                               
           (Ciba-Geigy)                                                   
                      95,000   95.3   120                                 
Weston 618 (GE)       99,000   95.1   100                                 
Sandostab P-EPQ                                                           
           (Sandoz)   108,000  94.7   110                                 
Weston TNPP                                                               
           (GE)       88,000   97.9   130                                 
PHENOLIC                                                                  
ANTI-                                                                     
OXIDANTS                                                                  
Irganox 1010                                                              
           (Ciba-Geigy)                                                   
                      95,000   97.5   110                                 
Cyanox 1790                                                               
           (Cyanamid) 98,000   96.9   120                                 
BHT                   87,000   96.5   130                                 
Irganox 1076                                                              
           (Ciba-Geigy)                                                   
                      121,000  97.8   130                                 
Topanol CA (ICI)      84,000   96.6   160                                 
AMINES                                                                    
Tinuvin 123                                                               
           (Ciba-Geigy)                                                   
                      65,000   94.8   70                                  
Tinuvin 622                                                               
           (Ciba-Geigy)                                                   
                      82,000   95.7   80                                  
Naugard 445                                                               
           (Uniroyal) 93,000   98.2   120                                 
THIOETHER                                                                 
Mark 2140  (Witco)    77,000   97.0   120                                 
METAL                                                                     
DE-                                                                       
ACTIVATORS                                                                
Irganox MD1024                                                            
           (Ciba-Geigy)                                                   
                      34,000   65.7   10                                  
Naugard XL-1                                                              
           (Uniroyal) 91,000   95.8   110                                 
______________________________________                                    
Note, that with a few exceptions, the phosphites and the phenolic antioxidants provide increased molecular weight with no reduction in polymerization rate. Of the amines, only Naugard® 445 provided stabilization without a rate decrease. The metal deactivators are expected to deactivate the catalyst, as was observed for Irganox® MD1024. The Naugard® XL-1 did not accomplish deactivation.
EXAMPLE 14 Polymer Melt Stability as a Function of Moisture Content
Lactide, produced and purified in a continuous (Gruber et al.) process, was fed at a rate of 3 kg/hr to a continuous polymerization pilot plant. Catalyst was added with a metering pump at the rate of 1 part catalyst to 5000 parts lactide on a molar basis. The reaction system was blanketed with nitrogen. The reactor vessels consist of two continuous stirred tank reactors (CSTR) in series. The first had a 1-gallon capacity and the second had a 5-gallon capacity. The reactors were run 60°-80 percent liquid filled and at 170°-180° C. Polymer melt pumps moved the liquid from CSTR 1 to CSTR 2, and from CSTR 2 through a die into a cooling water trough. The polymer strand thus produced was pulled from the trough by a pelletizer and stored as pellets.
The pelletized poly(lactide) was put into a drying hopper and dried at 40° C. under flowing dry air. Samples were pulled after one hour and four hours. These samples were then run through a single screw Brabender® extruder, with a retention time of approximately 3 minutes. Samples were analyzed for moisture by an automatic Karl Fischer apparatus and for molecular weight by GPC (the method of Example 7). The results of these tests are documented in Table 19 below.
              TABLE 19                                                    
______________________________________                                    
             Extruder     Weight Average                                  
Sample       Temperature (C.)                                             
                          Molecular Weight                                
______________________________________                                    
Initial                   63,000                                          
Dried 1 hour 137          44,000                                          
(1200 ppm H.sub.2 O)                                                      
             145          48,000                                          
             162          35,000                                          
             179          30,000                                          
Dried 4 hours                                                             
             140          63,000                                          
(150 ppm H.sub.2 O)                                                       
             140          69,000                                          
             160          65,000                                          
             178          68,000                                          
______________________________________                                    
These results show the detrimental effect of water in the lactide polymer resin during melt polymerization and the need to properly dry the poly(lactide) before melt-processing.
EXAMPLE 15 Degradation of Crystalline and Amorphous Poly(lactide)
Two literature references disclose poly(D,L-lactide) to degrade faster than poly(L-lactide), attributing the result to crystallinity of poly(L-lactide). These are: Kulkarni et al., J. Biomed. Mater. Res., vol. 5, pp. 169-181, (1971); Makino et al., Chem. Pharm. Bull., vol. 33, pp. 1195-201, (1985). An experiment was conducted to measure the effect of crystallinity on polymer degradation and is detailed below.
An amorphous poly(lactide) sample (clear, and less than 1 percent crystallinity based on DSC) and a crystalline poly(lactide) sample (opaque, and approximately 50 percent crystallinity based on DSC) were subjected to biodegradation in a compost test (50° C., with aeration).
The DSC apparatus was a TA Instruments, Inc., model 910 differential scanning calorimeter with DuPont 9900 computer support system typically programmed to heating at a rate of 10° C. per minute to 200° C. The samples had different optical composition, with the crystalline sample being more than 90 percent poly(L-lactide) and the amorphous sample being less than 80 percent poly(L-lactide) with the balance being either poly(D,L-lactide) or poly(meso-lactide). Samples of each polymer were subjected to a compost test (ASTM D 5338) which included mixing a stabilized compost and providing a source of humidified air while maintaining a temperature of about 50° C. The amorphous sample was completely degraded after 30 days of composting. The crystalline sample was only 23 percent degraded based on carbon dioxide after the same period of time.
Additional samples of these two polymers were subjected to chemical hydrolysis at 50° C. (hydrolysis is believed to be the rate-limiting step in the biodegradation process). The chemical hydrolysis procedure included placing 0.1 gram poly(lactide) in 100 ml of 0.2M phosphate buffer (pH=7.4). The samples were held for 1 week, then filtered, washed with deionized water, and dried at 25° C. under vacuum. The initial weight average molecular weight for each sample was about 70,000. After 1 week the amorphous sample had a weight average molecular weight of 10,000 and the crystalline sample had a weight average molecular weight of 45,000, determined by GPC (the method of Example 7). Neither sample had significant weight loss at this time.
Both of these tests demonstrate that degradation of crystalline poly(lactide) is slower than degradation of amorphous poly(lactide).
EXAMPLE 16 Effect of Monomer Concentration on Film Modulus
Poly(lactide) was precipitated in methanol from a chloroform solution in order to remove the residual lactide monomer. GPC analysis (the method of Example 1) showed the precipitated polymer to contain 0.0 percent lactide.
The polymer was dissolved in chloroform to make a 10 wt percent solution, and lactide was added back to make 5 separate solutions which, after removing the chloroform, are calculated to produce films containing 0.0, 0.2, 0.4, 1.0 and 4.0 weight percent lactide in poly(lactide). These solutions were solvent cast onto glass, dried overnight at room temperature in a fume hood, and removed to a vacuum oven. The films were hung in the vacuum oven and dried at 30° C. for 72 hours. GPC analysis of the vacuum-dried films showed measured lactide levels of 0.0, 0.0, 0.4, 0.7 and 3.7 wt percent.
The films were then tested for film modulus using ASTM procedure D882.
The results are shown below in Table 20.
              TABLE 20                                                    
______________________________________                                    
       Tensile        %           Elastic                                 
%      (psi    Std.   Elong-                                              
                            Std.  Modulus                                 
                                         Std.                             
Lactide                                                                   
       avg.)   Dev.   ation Dev.  (psi avg.)                              
                                         Dev.                             
______________________________________                                    
0      5490    636    2.85  0.14  730,000                                 
                                         103,000                          
0      6070    123    2.85  0.22  818,000                                 
                                         35,000                           
0.4    5670    227    2.75  0.27  779,000                                 
                                         44,000                           
0.7    5690    343    4.04  1.12  749,000                                 
                                         58,000                           
3.7    5570    458    3.33  1.43  738,000                                 
                                         66,000                           
______________________________________                                    
EXAMPLE 17 Rate of Water Uptake Versus Optical Composition
Samples of poly(lactide), made from 80 percent L-lactide and 20 percent of either D,L-lactide or meso-lactide, were ground to pass a 20 mesh screen. The samples were dried and devolatilized under vacuum then removed to a constant humidity chamber maintained at 24° C. and 50 percent relative humidity. The rate of moisture pick-up was determined gravimetrically, with the final results verified by Karl-Fischer water analysis. The rate of moisture pickup is shown below in Table 21.
              TABLE 21                                                    
______________________________________                                    
              Parts Per Million                                           
Time          Weight Gain                                                 
(Minutes)     L/D, L Polymer                                              
                           L/Meso Polymer                                 
______________________________________                                    
 10           600          1000                                           
 30           1100         1500                                           
 60           1500         1800                                           
120           1600         2100                                           
870           2100         2600                                           
Final (Karl-Fischer)                                                      
              3000         2600                                           
______________________________________                                    
EXAMPLE 18 Standard Test of Melt Stability
A standard test for determining melt stability is as follows:
A small sample (200 grams or less) of polymer is ground or pelletized and devolatilized by holding under vacuum (about 10 mm Hg) at a temperature of 130° C. or less for 18 hours. At this point the residual lactide content should be 1 wt percent or less. Portions (1-5 grams) of the devolatilized sample are then placed in a 16 ml sample vial, tightly capped, and placed in a 180° C. oil bath. Samples are removed at times of 15 minutes and 1 hour and analyzed for lactide content by GPC or other appropriate techniques. Lactide which may collect on the cooler portions of the vial is included in the product work-up and test.
Melt-stabilized poly(lactide) will show less than 2 percent lactide in the 15 minute sample, and more preferably less than 2 percent lactide in the 1 hour sample. The most highly stabilized poly(lactide)s will maintain lactide contents of less than 1 percent in both the 15 minute and 1 hour samples, preferably less than 0.5 percent. An unstabilized poly(lactide) may reach the equilibrium lactide content at 180° C. of 3.6 wt percent, or may go even higher as lactide is driven from the polymer melt and collects on the cooler top walls of the vial.
EXAMPLE 19 Water Scavenger Experiments
Dried poly(lactide) pellets were processed in a twin screw extruder to devolatilize and to prepare a portion with 0.5 percent by weight of a water scavenger (Stabaxol® P). The strands leaving the extruder are cooled in a water trough and chopped into pellets. Samples of the control and the test sample were then analyzed by the Karl Fischer technique for moisture content, with no drying. The control sample contained 1700 ppm water, the test sample had 450 ppm water. The control sample was then dried under nitrogen at 40° C., reducing the water content to 306 ppm. A vacuum-dried control sample had 700 ppm water.
The as-produced test sample and the dried control samples were then processed in a 1/2" single screw extruder (Brabender®) at 160° C., with a retention time of 3 minutes. The number average molecular weight for the dried control sample dropped from an initial value of 44,000 to a final value of 33,000 for the 306 ppm water sample and to 28,000 for the 700 ppm water sample. The test sample number average molecular weight dropped from an initial value of 40,000 to a final value of 33,000.
This sample shows how the water scavenger protected the polymer from moisture pick-up, imparting the same stability as a thorough drying of the control sample. Combining a water scavenger with appropriate drying is expected to give even greater stability.
EXAMPLE 20 Optimization of Catalyst Concentration
A mixture of 80 percent L-lactide and 20 percent D,L-lactide was polymerized using three different levels of tin(II) bis(2-ethyl hexanoate) catalyst. Batches were prepared at initial monomer/catalyst molar ratios of 1000:1, 3000:1, and 20,000:1. Polymerization times were adjusted to reach high conversion without being excessively long and thereby causing degradation in the melt. The reaction times were 1,2 and 20 hours, respectively. The polymerization temperature was 180° C. The polymers were ground to a coarse powder and devolatilized at 125° C. and 10 mm Hg overnight. The samples were then reground and 1-gram portions of each were placed into silanized vials, 16 ml capacity. The vials were sealed and placed into an oil bath at 180° C. Vials were then removed at various times and the samples were analyzed by GPC after dissolution in chloroform. The molecular weights and lactide contents are shown below in Table 22.
              TABLE 22                                                    
______________________________________                                    
                 Number     Weight                                        
                 Average    Average Lactide                               
         Time    Molecular  Molecular                                     
                                    Weight                                
Sample   (min)   Weight     Weight  %                                     
______________________________________                                    
1000:1   0       39,000     81,300  0.8                                   
         5       28,100     57,300  2.4                                   
         15      25,800     49,700  2.8                                   
         30      23,100     43,800  3.7                                   
         60      22,800     43,200  3.6                                   
3000:1   0       53,100     113,600 0.6                                   
         5       39,000     76,400  0.4                                   
         15      30,300     65,400  1.9                                   
         30      29,000     60,400  2.7                                   
         60      28,200     55,200  2.8                                   
20000:1  0       89,200     184,000 0.0                                   
         5       81,200     165,100 0.0                                   
         15      54,300     134,600 0.1                                   
         30      51,100     119,600 0.0                                   
         60      49,500     111,000 0.0                                   
______________________________________                                    
These results show the benefit of optimizing the catalyst level used in the polymerization process. Note that both lactide reformation and molecular weight retention benefits are realized from the reduced catalyst levels (higher monomer/catalyst ratio). It is believed catalyst levels should be limited to 0:1 for the high end of catalyst usage, with 3000:1 being more preferable and showing somewhat improved stability. Lower levels still, such as 20000:1, show greatly improved stability. Beyond this level it is believed the polymerization rates become too slow to be practical.
EXAMPLE 21 Removal of Tin Catalyst from Poly(lactide) by Precipitation
45 grams of L-lactide and 13 grams of D,L-lactide were charged with 78 milligrams of crystalline lactic acid to a ml round bottom flask. This was heated to 180° C. with magnetic stirring in an oil bath and blanketed with dry nitrogen. Catalyst in the form of tin(II) bis(2-ethyl hexanoate) was added as 0.20 ml of a 0.47 g/ml solution in THF after the molten lactide was at temperature. The mixture was allowed to stir for one minute and then pipetted into 3 silanized glass vials, which were then sealed and placed into a 180° C. oil bath for 75 minutes. The vials were allowed to cool and the polymer recovered by breaking the glass. The polymer was ground to a coarse powder and dissolved in chloroform to make a 10 percent solution. The polymer contained 3.8 percent residual monomer and had a number average molecular weight of 70,000 as determined by GPC measurement (the method of Example 7).
500 ml of methanol were placed in a 1-liter glass blender flask. The blender was turned on to medium speed and 50 ml of the polymer in chloroform solution was poured in over a period of three minutes. After one additional minute of blending the mixture was filtered, then rinsed with 100 ml of methanol, and dried overnight under vacuum. The polymer consisted of a fibrous mat. It contained 0.3 percent residual monomer and had a number average molecular weight of 66,900.
The measured tin level in the precipitated polymer was 337 ppm by weight, compared to a calculated value of 466 ppm for the as-produced polymer. This result indicates the feasibility of reducing residual catalyst levels in lactide polymers by solvent precipitation with the benefit of improved stability as detailed in Example 20.
EXAMPLE 22 Shear Rate
Samples of devolatilized poly(lactide) were tested in a Rosand Model 14° C. capillary rheometer. The die was 1 mm diameter and 16 mm long, with an entry angle of 180 degrees. The table below gives the pressure drop across the die as a function of nominal shear rate (not Rabinowitsch corrected) for various molecular weights and temperatures.
              TABLE 23                                                    
______________________________________                                    
                            Nominal Pressure                              
                            shear rate                                    
                                    Drop                                  
Mn     MW      Temp. (°C.)                                         
                            (s.sup.-1)                                    
                                    (MPa)                                 
______________________________________                                    
Results at 150° C.                                                 
34,000  70,000 150          192     2.0                                   
                            384      5.5                                  
                            960     10.0                                  
                            1920    13.8                                  
                            4800    19.7                                  
                            9600    23.7                                  
52,000 108,000 150          192     9.9                                   
                            384     15.6                                  
                            960     19.9                                  
                            1920    23.9                                  
                            4800    29.4                                  
                            9600    --                                    
60,000 137,000 150          192     7.4                                   
                            384     11.1                                  
                            960     16.6                                  
                            1920    21.0                                  
                            4800    --                                    
                            9600    --                                    
183,000                                                                   
       475,000 150          192     19.1                                  
                            384     27.0                                  
                            960     31.4                                  
                            1920    --                                    
                            4800    --                                    
                            9600    --                                    
Results at 175° C.                                                 
34,000  70,000 175          192     0.4                                   
                            384     0.5                                   
                            960     3.4                                   
                            1920    5.5                                   
                            4800    9.2                                   
                            9600    12.5                                  
52,000 108,000 175          192     2.2                                   
                            384     4.6                                   
                            960     7.6                                   
                            1920    11.5                                  
                            4800    17.2                                  
                            9600    22.1                                  
183,000                                                                   
       475,000 175          192     11.5                                  
                            384     16.6                                  
                            960     20.2                                  
                            1920    24.4                                  
                            4800    29.9                                  
                            9600    --                                    
Results at 200° C.                                                 
60,000 137,000 200          192     0.5                                   
                            384     1.6                                   
                            960     3.3                                   
                            1920    5.3                                   
                            4800    --                                    
                            9600    13.2                                  
183,000                                                                   
       475,000 200          192     7.0                                   
                            384     11.0                                  
                            960     14.2                                  
                            1920    17.9                                  
                            4800    21.6                                  
                            9600    --                                    
______________________________________                                    
EXAMPLE 23 Effect of Meso-lactide Concentration on Rate of Crystallization
Polymer samples of various optical compositions were prepared by polymerizing mixtures of L-lactide and meso-lactide with tin(II)bis(2-ethyl hexanoate) catalyst at a temperature of about 180° C. A portion of each sample was tested in a Mettler Differential Scanning Calorimeter (DSC), Model 30, by heating from 60° C. to 200° C. at 20° C./minute. The sample was then held at 200° C. for 2 minutes to completely melt any crystals. The samples were then quenched to the annealing temperature of interest and held minutes. The samples were then quenched to 60° C. and reheated at 20° C./minute to 200° C. to determine the crystallinity. The crystallinity of the sample following annealing is proportional to the energy of the melting endotherm minus any crystallization exotherm.
              TABLE 24                                                    
______________________________________                                    
Net endotherm following 15 minute annealing                               
at given temperature (J/gm)                                               
Sample      Temperature =                                                 
                        Temperature =                                     
(% meso)    85° C.                                                 
                        110° C.                                    
______________________________________                                    
0           34.3        48.4                                              
3           5.1         48.2                                              
6           0.1         14.5                                              
9           0.3         11.0                                              
______________________________________                                    
The results show that introducing meso-lactide greatly reduces the rate of crystallization for poly(lactide). Therefore, control of the meso level and tailoring the processing conditions are important.
EXAMPLE 24 The Effect of Meso-lactide Concentration on Crystallization
Samples of devolatilized poly(lactide) of varying optical composition and with number average molecular weights in the range of 50,000 to 130,000 were prepared in a continuous pilot plant. The samples were dissolved in chloroform to a concentration of 5 grams/100cc and the optical rotation of the samples was measured to determine the concentration of meso-lactide which had been present in the monomer mixture prior to polymerization. Separate optical rotation and gas chromatography analysis of the monomer mixture confirmed that L-lactide and meso-lactide are the predominate components when meso-lactide is present at a concentration of 20 percent or less, and only a small correction is required for D-lactide.
Additional samples were made by polymerizing mixtures with known weights of L-lactide and meso-lactide.
All samples were subjected to an annealing procedure to develop crystallinity. The annealing procedure consisted of placing the samples in an oven at 100°-105° C. for 90 minutes, then lowering the temperature 10° C. each 1/2 hour until the temperature reached 45° C. The oven was then shut off and the samples were allowed to cool to room temperature. The energy of the melting endotherm and the peak melting temperature were then measured using a Mettler Differential Scanning Calorimeter (DSC) apparatus with a scan speed of 20° C./minute. The energy of melting is a measure of crystallinity in the annealed samples.
FIG. 3 shows sharp decline in crystallinity between 9 and 12 percent meso content.
EXAMPLE 25 Effect of Plasticizer on Crystallization Rate
Devolatilized polymer samples from a continuous pilot plant were compounded with dioctyl adipate (a plasticizing agent) and/or silica in a twin screw extruder. The samples were then tested from crystallization rate using the DSC of Example 23. In this case the DSC program included a first upheat, in which the samples were heated from -20° C. to 200° C. at a rate of 20° C./minute, holding at 200° C. for 2 minutes, quenching, and a second upheat from -20° C. to 200° C. at 20° C./minute. The energy of the crystallization exotherm, occurring at a temperature from about 75° C. to about 115° C., is proportional to the amount of crystallization which occurs during this two minute period.
The table below shows the increased crystallization observed when the plasticizer dioctyl adipate (DOA) is present, either with or without silica present. The base polymer, without plasticizer, shows no crystallization during the DSC upheat. The exotherms are reported on a joules per gram of poly(lactide) basis (filler free basis).
              TABLE 25                                                    
______________________________________                                    
              First Upheat Second Upheat                                  
Sample        Exotherm (J/gm)                                             
                           Exotherm (J/gm)                                
______________________________________                                    
Base polymer  0            0                                              
Base polymer +                                                            
              26.7         27.2                                           
8 wt % DOA                                                                
Base polymer +                                                            
              4.0          0                                              
40 wt % silica                                                            
Base polymer +                                                            
              27.1         27.6                                           
40 wt % silica +                                                          
5 wt % DOA                                                                
______________________________________                                    
EXAMPLE 26 An Evaluation of Nucleating Agents
A devolatilized sample of poly(lactide) polymer was compounded with a variety of potential nucleating agents in a single screw extruder. The candidate nucleating agents were added at a nominal level of 5 percent by weight. The single screw extruder is not as effective of a mixer as would be used commercially, so failure to observe an effect in these tests does not mean that a candidate agent would not be effective if blended more thoroughly. A positive result in this test demonstrates potential ability to increase crystallization rates. Additives which increased crystallinity in the second upheat (on a quenched sample) were rated ++, additives which showed an effect only on the first upheat were rated +, and additives which showed no effect were rated 0.
              TABLE 26                                                    
______________________________________                                    
Additive                Effect                                            
______________________________________                                    
None                    0                                                 
talc, MP1250 (Pfizer)   ++                                                
3-nitro benzoic acid    0                                                 
saccharin, sodium salt  ++                                                
terephthalic acid,      0                                                 
disodium salt                                                             
calcium silicate, -200 mesh                                               
                        +                                                 
sodium benzoate         +                                                 
calcium titanate, -325 mesh                                               
                        +                                                 
boron nitride           +                                                 
calcium carbonate, 0.7 micron                                             
                        0                                                 
copper phthalocyanine   +                                                 
saccharin               0                                                 
low molecular weight polyethylene                                         
                        0                                                 
talc, Microtuff-F (Pfizer)                                                
                        ++                                                
talc, Ultratalc (Pfizer)                                                  
                        ++                                                
ethylene acrylic acid sodium ionomer                                      
                        0                                                 
(Allied Signal)                                                           
isotactic polypropylene +                                                 
polyethylene terephthalate                                                
                        0                                                 
crystalline poly(L-lactide) (low mol. wt.)                                
                        ++                                                
Millad 3940 (Milliken)  ++                                                
Millad 3905 (Milliken)  +                                                 
NC-4 (Mitsui)           +                                                 
polybutylene terephthalate                                                
                        +                                                 
talc in polystyrene (Polycom Huntsman)                                    
                        +                                                 
talc in polyethylene (Advanced                                            
                        ++                                                
Compounding)                                                              
______________________________________                                    
EXAMPLE 27 Heat Set Crystallization of an Oriented Poly(lactide) Film
Two film samples, one non-oriented and the other biaxially oriented, were constrained in a film holder and annealed for either 5 minutes or 15 minutes in an oil bath at 85° C. The extent of crystallization was determined by DSC from the melting endotherm of the crystalline domains formed during the annealing, using a ramp rate of 20° C./minute. The biaxially oriented film developed significantly more crystallinity for each time, as shown in the table below.
              TABLE 27                                                    
______________________________________                                    
       t = 0 minutes                                                      
                    t = 5 minutes                                         
                               t = 15 minutes                             
       endotherm    endotherm  endotherm                                  
Sample (J/gm)       (J/gm)     (J/gm)                                     
______________________________________                                    
non-   0.6          0.0        0.8                                        
oriented                                                                  
biaxially                                                                 
       0.7          8.1        8.5                                        
oriented                                                                  
______________________________________                                    
Each of the films was made from lactide mixtures containing an estimated meso-lactide content of about 12 wt %, with about 88 wt % L-lactide. When subjected to the slow oven annealing procedure of Example 24, samples from both of the films developed crystallinity which gave a melting endotherm of about 25 J/gm. The biaxially oriented film had been stretched approximately 4× in the machine direction and 2× in the transverse direction (using a tenter frame), all at about 63°-74° C.
EXAMPLE 28 Properties of PLA-cellulose Acetate Blends
In the twin screw extruder described in Example 1, poly(lactide) was blended with cellulose acetate (Tenite 110 from Eastman), cellulose acetate propionate (Tenite 375 from Eastman), and cellulose butyrate (Tenite 575 from Eastman) in levels shown in Table 28. The poly(lactide) had a weight average molecular weight of about 200,000, a meso content of about 10.5%, a residual lactide level of about 0.3%, and a moisture content less than about 300 ppm. The weight percentages of poly(lactide) and cellulose derivatives is shown in the following table:
                                  TABLE 28                                
__________________________________________________________________________
Composition                                                               
       1   2  3  4  5  6  7  8  9  10                                     
__________________________________________________________________________
CA         20%                                                            
              50%                                                         
                 80%                                                      
CAP                 20%                                                   
                       50%                                                
                          80%                                             
CAB                          20%                                          
                                50%                                       
                                   80%                                    
PLA    100%                                                               
           80%                                                            
              50%                                                         
                 20%                                                      
                    80%                                                   
                       50%                                                
                          20%                                             
                             80%                                          
                                50%                                       
                                   20%                                    
__________________________________________________________________________
The blends were prepared using a melt temperature of 190°-200° C., die pressure of 18-20 bar, and a screw speed of 250 rpm. All materials but one were pelletized, dried and injection molded into a standard ASTM test specimen mold for testing. Composition 3 was not pelletized due to poor strength of the extruded polymer stand. This is evidence of mechanical incompatibility of the cellulose acetate and poly(lactide). The remaining compositions were tested for tensile strength and elongation to break in accord with ASTM D 638-91 and heat distortion temperature according to ASTM D 648-82.
Another test performed on each sample was a test for resistance to hot water. A standard tensile bar is placed in a hot water bath at 190° F. for 3 minutes. The sample is removed from the water and placed in a horizontal position with the flat sides facing up and down with one end of the tensile bar held in a clamp. Samples which have softened as a result of the hot water exposure will bend under the force of gravity. The degree of bend is measured using a protractor. The maximum degree of bend is 90° and constitutes a failure. The best result is no bend of the sample.
The test results are shown in the following table:
              TABLE 29                                                    
______________________________________                                    
                          Heat     Hot                                    
      Tensile   Elongation                                                
                          distortion                                      
                                   water test                             
      strength to                                                         
                to        temperature                                     
                                   angle of                               
Sample                                                                    
      break (psi)                                                         
                break (%) (°C.)                                    
                                   (deformation)                          
______________________________________                                    
1     7100      5.4       51.1     46°                             
2     5900      1.5       41.7     44°                             
3     --        --        --       --                                     
4 10  3200      2.2       --        0°                             
5     8100      2.2       46.7     10°                             
6     5600      6.9       45.7      3°                             
7     4700      17.9      50.0      0°                             
8     7600      2.3       48.2     23°                             
9 15  5500      8.3       --        0°                             
10    5100      17.9      51.9      0°                             
______________________________________                                    
These results show that many compositions of poly(lactide) blended with CA, CAP and CAB are compatible enough to exhibit good physical properties. Blends of PLA with high loadings of CAP and CAB may increase the flexibility of unblended poly(lactide). Resistance of poly(lactide) to hot water was dramatically increased by addition of CA, CAP or CAB.
EXAMPLE 29 Heat Sealability of a Poly(lactide) Film
Poly(lactide) with a weight average MW of 160,000, a meso content of 8 to 12%, and a moisture level of about 200 ppm was extruded into film using the same method as Example 2.
Two pieces of the poly(lactide) film were heat sealed in an Accuseal Heat Sealer Model 30 having heated platens of a dimension of 1/4"×25". The temperature and dwell time were varied to find the minimum time required to form a bond between the films. The pressure was 40 psi. Bond strength was estimated by pulling the two films apart 10 seconds after sealing and judging pass or fail. Either the films tore before the bond failed (pass) or the films separated at the bondline (fail). Results are shown below:
              TABLE 29                                                    
______________________________________                                    
Temperature (C.°)                                                  
Time                                                                      
(sec) 30    40     50  60    65  70    75  80   85  90                    
______________________________________                                    
1     F     F                                                             
2                  F   F     F   P     P                                  
3                      F                   P    P                         
4                            P                      P                     
5                                          P                              
6                                                   P                     
______________________________________                                    
Sealing conditions of 70° C. at a line pressure of 40 psi for a 2 second dwell time were found to be sufficient for forming a good bond between the two poly(lactide) films.
EXAMPLE 30 Effect of Talc on Crystallization Rate of Poly(lactide).
Poly(lactide) prepared in a continuous pilot plant, from a lactide mixture with an approximate composition of L-lactide and 9% meso-lactide, was dried and devolatilized in a twin screw extruder. The polymer was then redried and talc (Ultratalc 609, from Pfizer) was compounded in at levels from 2 wt % to 21 wt %. Samples of the compounded poly(lactide) were placed in a DSC apparatus and subjected to a heating program consisting of a first upheat from 60° C. to 200° C. for two minutes, quenching to 90° C., holding at 90° C. for 15 minutes, followed by a quench and second upheat from 60° C. to 200° C. The first upheat and quench is to make each of the samples amorphous, the crystallization exotherm is measured during the 90° C. isothermal run, and the second upheat is used to confirm the isothermal exotherm through a direct measurement of the melting endotherm of the crystalline domains formed during the isothermal annealing.
The table below shows the extent of crystallization (reported on talc free basis) as a function of time for various talc loadings. The results show that talc significantly increases the rate of crystallization of the poly(lactide).
              TABLE 30                                                    
______________________________________                                    
                             2nd                                          
       Exotherm (J/gm of PLA) to time                                     
                             upheat                                       
Sample   2 min.  5 min.  8 min.                                           
                               12 min.                                    
                                     15 min.                              
                                           J/gm)                          
______________________________________                                    
PLA      0       0       0     0     0     0                              
PLA + 2  0.1     0.6     1.1   4.2   7.9   10.0                           
wt % talc                                                                 
PLA + 6  0.5     2.6     5.3   11.8  17.2  21.2                           
wt % talc                                                                 
PLA + 11 0.8     2.5     10.8  22.2  27.3  28.2                           
wt % talc                                                                 
PLA + 21 2.3     11.3    19.2  25.4  27.6  26.2                           
wt % talc                                                                 
______________________________________                                    
EXAMPLE 31 Stress-induced Crystallization of a Poly(lactide) Sheet
Poly(lactide), copolymerized with 0.55 wt % epoxidized linseed oil, from a continuous pilot plant was dried, devolatilized, redried, and compounded with 25 wt % talc (Ultratalc 609, Pfizer) and 25 wt % plasticizer (Citroflex A-4, Morflex). This material was then dried and cast into a 15 mil sheet. Strips of the sheet, approximate 1"×4", were loaded into an MTS test instrument using a 1" gap width and stretched to about 4× at room temperature. After stretching, the test samples were removed from the MTS and analyzed by a DSC to determine the amount of stress-induced crystallization, using the net melting endotherm. Crystallization exotherms were not observed for these samples, except for the unstretched control.
              TABLE 31                                                    
______________________________________                                    
Sample (stretching speed)                                                 
                 Melting endotherm (J/gm)                                 
______________________________________                                    
unstretched (control)                                                     
                 2.4 (net, after subtracting                              
                 crystallization exotherm)                                
 5 mm/sec (nominal)                                                       
                 19.1                                                     
26 mm/sec (estimated)                                                     
                 17.3                                                     
26 mm sec (estimated)                                                     
                 19.2                                                     
26 mm sec (estimated)                                                     
                 17.5                                                     
26 mm sec (estimated)                                                     
                 18.3 (sample tore at end of test)                        
______________________________________                                    
Each of the stretched samples showed a pronounced development of stress-included crystallization.
EXAMPLE 32 Stress-induced Crystallization of a Poly(lactide) Film
Poly(lactide), copolymerized with 0.55 wt % epoxidized linseed oil, was dried, devolatilized, and redried. The lactide had a meso-lactide content of about 8-10%. The material was then cast into 15 mil sheet. Squares of the material, approximately 5"×5", were stretched using an Iwamoto biaxial stretcher either in a single direction or biaxially. The stretching temperature was 65° C. and the stretching speed was 10 mm/s. The stretched films were tested by DSC to determine the extent of crystallization.
              TABLE 32                                                    
______________________________________                                    
      Cold Crystallization                                                
                      Melting       Net                                   
Sample                                                                    
      Exotherm (J/gm) Endotherm (J/gm)                                    
                                    J/gm                                  
______________________________________                                    
1 × 2                                                               
      1.2             1.7           0.5                                   
1 × 3                                                               
      16.4            23.7          7.3                                   
1 × 4                                                               
      12.6            19.9          7.3                                   
4 × 4                                                               
      17.7            22.6          4.9                                   
______________________________________                                    
EXAMPLE 33 Heat-set Crystallization of an Oriented Poly(lactide Film
The biaxially oriented sample (4×4) of Example 32 was constrained in a film holder and annealed at 85° C. for one minute. The annealed sample had a cold crystallization exotherm of 1.3 J/gm, a melting endotherm of 21.6 J/gm, and a net endotherm of 20.3 J/gm. For comparison, Example 23 shows that a non-oriented sample of comparable meso content has a net endotherm of less than 1 J/gm after 15 minutes of annealing at 85° C.
EXAMPLE 34 Crystallization of Pellets and Films During Storage
The talc filled, plasticized, pellets and unoriented films of Example 31 were stored at room temperature for 12 days and 11 days, respectively. They were then retested by DSC to determine if any crystallization had taken place during storage. Significant crystallization had occurred, and the feed pellets showed a melting endotherm of 17.4 J/gm and the film showed a melting endotherm of 18.8 J/gm on an as-tested basis. This corresponds to 35 J/gm and 38 J/gm on a poly(lactide) basis. No crystallization exotherms were observed during the DSC upheat.
EXAMPLE 35 Stress-induced Crystallization and Strain Hardening of a Poly(lactide) Film
Additional samples of the polymer film used in Example 32 were subjected to uniaxial stretching on the Iwamoto biaxial stretcher. The polymer, after melting and quenching, exhibited a Tg with an inflection point of 59° C. when tested by DSC at a scan rate of 20° C./min. The samples were stretched at various temperatures at a rate of 99 mm/sec and tested by DSC to determine the extent of crystallization. Force curves for the stretching operation were also recorded.
              TABLE 33                                                    
______________________________________                                    
Stretching                                                                
          Net Melting                                                     
                     Stretching Force (kg) needed                         
Temperature                                                               
          Endotherm  at elongation of                                     
(°C.)                                                              
          (J/gm)     initial 200%  300%  400%                             
______________________________________                                    
68        18         28      24    27    49                               
72        18         26      30    40    52                               
76        20         14      14    14    16                               
80        8          11      11    12    16                               
______________________________________                                    
The table above shows the development of stress induced crystallinity when the polymer was stretched at temperatures up to 20° C. above Tg. At 80° C. less stress induced crystallinity developed, although the sample crystallized readily during subsequent annealing. The samples stretched at 68° C. and 72° C. show pronounced strain hardening at 300-400% elongation during this test. The samples stretched at higher temperatures did not show the same degree of strain hardening.
It will be understood that even though these numerous characteristics and advantages of the invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of the parts or in the sequence or the timing of the steps, within the broad principle of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims (49)

What is claimed:
1. A semi-crystalline film exhibiting a net endotherm greater than about 10 joules per gram of poly(lactide) polymer, comprising a melt stable polymer composition, said composition comprising:
i) a plurality of poly(lactide) polymer chains, said polymer chains being reaction products of polymerizing a lactide mixture comprising less than about 15 percent by weight meso-lactide, with the remaining lactide being selected from the group consisting of L-lactide, D-lactide and mixtures thereof, whereby at least about 85% of the lactide is either L-lactide or D-lactide, said plurality having a number average molecular weight of from about 10,000 to about 300,000;
ii) residual lactide in a concentration of less than about 2 percent by weight; and
iii) water, if present at all, present in a concentration of less than about 2000 parts per million.
2. The film of claim 1 wherein said plurality of poly(lactide) polymer chains have a number average molecular weight from about 20,000 to about 275,000.
3. The film of claim 1 wherein said plurality of poly(lactide) polymer chains have a number average molecular weight from about 40,000 to about 250,000.
4. The film of claim 1 wherein said polymer chains are reaction products of polymerizing a lactide mixture comprising less than about 9 percent by weight meso-lactide.
5. The film of claim 1 wherein said concentration of water is less than about 500 parts per million.
6. The film of claim 1 wherein said concentration of water is less than about 100 parts per million.
7. The film of claim 1 wherein said polymer composition further comprises a stabilizing agent.
8. The film of claim 7 wherein said stabilizing agent is an antioxidant.
9. The film of claim 7 wherein said stabilizing agent is a water scavenger.
10. The film of claim 8, wherein said antioxidant comprises a phosphite-containing compound.
11. The film of claim 8, wherein said antioxidant comprises a hindered phenolic or phenolic compound.
12. The film of claim 8, wherein said antioxidant is selected from the group consisting of trialkyl phosphites, mixed alkyl/aryl phosphites, alkylated aryl phosphites, sterically hindered aryl phosphites, aliphatic spirocyclic phosphites, sterically hindered phenyl spirocyclics, sterically hindered bisphosphonites, hydroxyphenyl propionates, hydroxy benzyls, alkylidene bisphenols, alkyl phenols, aromatic amines, thioethers, hindered amines, hydroquinones and mixtures thereof.
13. The film of claim 9, wherein said water scavenger is selected from the group consisting of carbodiimides, anhydrides, acyl chlorides, isocyanates, alkoxy silanes and mixtures thereof.
14. The film of claim 9, wherein said water scavenger is a desiccant selected from the group consisting of clay, alumina, silica gel, zeolites, calcium chloride, calcium carbonates, sodium sulfate, bicarbonates and mixtures thereof.
15. The film of claim 1 wherein said polymer composition further comprises:
iv) catalyst means for catalyzing the polymerization of lactide to form the poly(lactide) polymer chains, said catalyst means incorporated into the melt-stable lactide polymer composition during polymerization.
16. The film of claim 1 wherein said plurality of poly(lactide) polymer chains is the reaction product of polymerization at a temperature greater than about 160° C.
17. The film of claim 1 wherein said polymer composition further comprises a plasticizer selected from the group consisting of alkyl phosphate esters, dialkylether diesters, tricarboxylic esters, epoxidized oils and esters, polymeric polyesters, polyglycol diesters, alkyl alkylether diesters, aliphatic diesters, alkylether monoesters, citrate esters, dicarboxylic esters, esters of glycerine and mixtures thereof.
18. The film of claim 1 wherein said polymer composition further comprises a nucleating agent which is a crystalline polymer with a melting point greater than the processing temperature of the poly(lactide).
19. The film of claim 1 wherein said polymer composition further comprises a pigment selected from the group consisting of titanium dioxide, clays, calcium carbonate, talc, mica, silica, iron oxide, iron hydroxide, carbon black, magnesium oxide and mixtures thereof.
20. A semi-crystalline poly(lactide) film wherein a substantial portion of crystallinity was induced through orientation.
21. The film of claim 20 wherein said orientation is in a plurality of directions.
22. A semi-crystalline film comprising:
(i) 50 to 85% by weight of a semi-crystalline lactide polymer composition exhibiting a net endotherm greater than about 10 joules per gram of poly(lactide) polymer;
(ii) 15 to 30% by weight of a plasticizer; and
(iii) 0 to 20% by weight of a filler.
23. A semi-crystalline film made of poly(lactide) or poly(lactic acid) wherein sequences of the major lactic acid conformation have at least a 0.5 probability of comprising at least ten lactic acid residuals.
24. The film of claim 23 wherein the sequences of the minor component have less than 0.01 probability of comprising at least three lactic acid residuals.
25. A process for the manufacture of a semi-crystalline film exhibiting a net endotherm greater than about 10 joules per gram of poly(lactide) polymer, said process comprising the steps of:
a) providing a melt-stable lactide polymer composition comprising:
i) a plurality of poly(lactide) polymer chains, said plurality of polymer chains being reaction products of polymerizing a lactide mixture comprising less than about 15 percent by weight meso-lactide, with the remaining lactide being selected from the group consisting of L-lactide, D-lactide and mixtures thereof, whereby at least about 85% of the lactide is either L-lactide or D-lactide, said plurality of polymer chains having a number average molecular weight of about 10,000 to about 300,000;
ii) lactide in a concentration of less than about 2 percent by weight; and
iii) water, if present at all, present in a concentration of less than about 2000 parts per million; and
b) extruding said polymer composition into a film.
26. The process of claim 25 wherein said polymer chains are reaction products of polymerizing a lactide mixture comprising less than about 9 percent by weight meso-lactide.
27. The process of claim 25 wherein said concentration of water is less than about 100 parts per million.
28. The process of claim 25 wherein said polymer composition further comprises a stabilizing agent.
29. The process of claim 28 wherein said stabilizing agent is an antioxidant.
30. The process of claim 28 wherein said stabilizing agent is a water scavenger.
31. The process of claim 29 wherein said antioxidant is a phosphite-containing compound.
32. The process of claim 29 wherein said antioxidant is a hindered phenolic or phenolic compound.
33. The process of claim 29 wherein said antioxidant is selected from the group consisting of trialkyl phosphites, mixed alkyl/aryl phosphites, alkylated aryl phosphites, sterically hindered aryl phosphites, aliphatic spirocyclic phosphites, sterically hindered phenyl spirocyclics, sterically hindered bisphosphonites, hydroxyphenyl propionates, hydroxy benzyls, alkylidene bisphenols, alkyl phenols, aromatic amines, thioethers, hindered amines, hydroquinones and mixtures thereof.
34. The process of claim 30 wherein said water scavenger is selected from the group consisting of carbodiimides, anhydrides, acyl chlorides, isocyanates, alkoxy silanes and mixtures thereof.
35. The process of claim 30 wherein said water scavenger is a desiccant selected from the group consisting of clay, alumina, silica gel, zeolites, calcium chloride, calcium carbonates, sodium sulfate, bicarbonates and mixtures thereof.
36. The process of claim 25 wherein said polymer composition further comprises:
(iv) catalyst means for catalyzing the polymerization of lactide to form the poly(lactide) polymer chains, said catalyst means incorporated into the melt-stable lactide polymer composition during polymerization.
37. The process of claim 25 wherein said plurality of poly(lactide) polymer chains are the reaction products of polymerization at a temperature of greater than about 160° C.
38. The process of claim 25 further comprising the step of:
(c) orienting the film.
39. The process of claim 38 wherein the orientation step induces crystallinity.
40. The process of claim 38 further comprising the step of:
(d) heat setting the film.
41. A process for the manufacture of a semi-crystalline film, said process comprising the steps of:
(a) providing a composition comprising:
(i) 50 to 85% by weight of a semi-crystalline lactide polymer composition exhibiting an endotherm greater than about 10 joules per gram of poly(lactide) polymer;
(ii) about 15 to 30% by weight of a plasticizer;
(iii) up to 20% by weight of a filler;
(b) extruding said composition into a semi-crystalline film;
(c) orienting said film in either the machine direction, the cross direction, or both directions by stretching the film at least 1.1 times its original size.
42. An article comprising a semi-crystalline film exhibiting a net endotherm greater than about 10 joules per gram of poly(lactide) polymer, comprising a melt stable polymer composition, said composition comprising:
i) a plurality of poly(lactide) polymer chains, said polymer chains being reaction products of polymerizing a lactide mixture comprising less than about 15 percent by weight meso-lactide, with the remaining lactide being selected from the group consisting of L-lactide, D-lactide and mixtures thereof, whereby at least about 85% of the lactide is either L-lactide or D-lactide, said plurality having a number average molecular weight of from about 10,000 to about 300,000;
ii) residual lactide in a concentration of less than about 2 percent by weight; and
iii) water, if present at all, present in a concentration of less than about 2000 parts per million.
43. The article according to claim 42, said article being a diaper.
44. The article according to claim 42, said article being a packaging film.
45. The article according to claim 42, said article being an agricultural mulch film.
46. The article according to claim 42, said article being a shrink wrap film.
47. The article according to claim 42, said article being a bag.
48. The article according to claim 42, said article being a tape.
49. The film of claim 1 wherein said polymer composition further comprises a filler selected from the group consisting of cellulose, wheat, starch, modified starch, chitin, chitosin, keratin, cellulose acetate, cellulosic materials derived from agricultural products, gluten, net shell flour, wood flour, corn cob flour, guar gum, talc, silica, mica, kaolin, titanium dioxide, wollastonite, perlite, diatomaceous earth and mixtures thereof.
US08/110,394 1992-10-02 1993-08-23 Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof Expired - Lifetime US5536807A (en)

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US08/110,394 US5536807A (en) 1992-10-02 1993-08-23 Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
DE69328018T DE69328018T2 (en) 1992-10-02 1993-09-30 MELT-STABLE LACTIDE POLYMER FILMS AND METHOD FOR THEIR PRODUCTION
PCT/US1993/009331 WO1994007941A1 (en) 1992-10-02 1993-09-30 Melt-stable lactide polymer films and processes for manufacture thereof
AU52953/93A AU5295393A (en) 1992-10-02 1993-09-30 Melt-stable lactide polymer films and processes for manufacture thereof
AT93923183T ATE190337T1 (en) 1992-10-02 1993-09-30 MELTSABLE LACTIDE POLYMER FILM AND METHOD FOR THE PRODUCTION THEREOF
NZ256972A NZ256972A (en) 1992-10-02 1993-09-30 Film formed from melt-stable poly(lactide) composition, the poly(lactide) having a number average molecular weight of at least 10,000
ES93923183T ES2142880T3 (en) 1992-10-02 1993-09-30 LACTIDE POLYMER FILMS STABLE TO MELTING AND PROCEDURE FOR ITS MANUFACTURE.
KR1019940701867A KR100326642B1 (en) 1992-10-02 1993-09-30 Melt-stable lactide polymer films and preparation methods thereof
JP50932194A JP3436368B2 (en) 1992-10-02 1993-09-30 Melt-stable lactide polymer film and method for producing the same
CA002124847A CA2124847C (en) 1992-10-02 1993-09-30 Melt-stable lactide polymer films and processes for manufacture thereof
BR9305660A BR9305660A (en) 1992-10-02 1993-09-30 Stable fusion lactide polymer films and processes for their manufacture
EP93923183A EP0615529B1 (en) 1992-10-02 1993-09-30 Melt-stable lactide polymer films and processes for manufacture thereof
FI942559A FI942559A (en) 1992-10-02 1994-05-31 Melt-stable lactide polymer films and a method for their preparation
NO942038A NO942038L (en) 1992-10-02 1994-06-01 Melt-stable lactide polymer films and processes for their preparation
US08/607,090 US5773562A (en) 1992-10-02 1996-02-28 Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
US09/036,799 US6093791A (en) 1992-10-02 1998-03-09 Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
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US09/286,784 Expired - Lifetime US6197380B1 (en) 1992-10-02 1999-04-06 Paper having a melt-stable lactide polymer coating and process for manufacture thereof
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US09/361,375 Expired - Lifetime US6121410A (en) 1992-10-02 1999-07-27 Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof

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Cited By (110)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5773562A (en) * 1992-10-02 1998-06-30 Cargill, Incorporated Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
US5849401A (en) * 1995-09-28 1998-12-15 Cargill, Incorporated Compostable multilayer structures, methods for manufacture, and articles prepared therefrom
US5849374A (en) * 1995-09-28 1998-12-15 Cargill, Incorporated Compostable multilayer structures, methods for manufacture, and articles prepared therefrom
US5866634A (en) * 1995-09-25 1999-02-02 Shin-Etsu Chemical Co., Ltd Biodegradable polymer compositions and shrink films
US5895587A (en) * 1997-01-21 1999-04-20 Cryovac, Inc. Cook-in package and method of making same
US6114495A (en) * 1998-04-01 2000-09-05 Cargill Incorporated Lactic acid residue containing polymer composition and product having improved stability, and method for preparation and use thereof
US6123811A (en) * 1998-12-14 2000-09-26 Ethicon, Inc. Method of manufacturing aqueous paper pulp for water soluble packages
US6183814B1 (en) 1997-05-23 2001-02-06 Cargill, Incorporated Coating grade polylactide and coated paper, preparation and uses thereof, and articles prepared therefrom
US6229046B1 (en) 1997-10-14 2001-05-08 Cargill, Incorported Lactic acid processing methods arrangements and products
US6475759B1 (en) 1997-10-14 2002-11-05 Cargill, Inc. Low PH lactic acid fermentation
US6506873B1 (en) 1997-05-02 2003-01-14 Cargill, Incorporated Degradable polymer fibers; preparation product; and, methods of use
US6672001B1 (en) * 1998-11-17 2004-01-06 Board Of Regents Of University Of Nebraska Method for mulching an agricultural soil bed using a biodegradable protein material, and a mulched agricultural crop growing plot produced thereby
US20040005677A1 (en) * 2002-07-05 2004-01-08 Eddington John M. Novel lactobacillus strains and use thereof in fermentation process for L-lactic acid production
US20040176513A1 (en) * 2002-10-24 2004-09-09 Mukerrem Cakmak Process for making strain-hardened polymer products
US20040209073A1 (en) * 2001-06-06 2004-10-21 Sonja Rosenbaum Biodegradable biaxially drawn film with controlled tear resistance
US20040214724A1 (en) * 2001-06-11 2004-10-28 Todd Bradley L. Compositions and methods for reducing the viscosity of a fluid
US20040261993A1 (en) * 2003-06-27 2004-12-30 Nguyen Philip D. Permeable cement and sand control methods utilizing permeable cement in subterranean well bores
US20040261999A1 (en) * 2003-06-27 2004-12-30 Nguyen Philip D. Permeable cement and methods of fracturing utilizing permeable cement in subterranean well bores
US20040261996A1 (en) * 2003-06-27 2004-12-30 Trinidad Munoz Methods of diverting treating fluids in subterranean zones and degradable diverting materials
US20040261995A1 (en) * 2003-06-27 2004-12-30 Nguyen Philip D. Compositions and methods for improving proppant pack permeability and fracture conductivity in a subterranean well
US20050008815A1 (en) * 2001-11-01 2005-01-13 Masayuki Sukigara Biaxially oriented polylactic acid-based resin films
US20050028976A1 (en) * 2003-08-05 2005-02-10 Nguyen Philip D. Compositions and methods for controlling the release of chemicals placed on particulates
US20050034868A1 (en) * 2003-08-14 2005-02-17 Frost Keith A. Orthoester compositions and methods of use in subterranean applications
US20050034865A1 (en) * 2003-08-14 2005-02-17 Todd Bradley L. Compositions and methods for degrading filter cake
US20050045328A1 (en) * 2001-06-11 2005-03-03 Frost Keith A. Orthoester compositions and methods for reducing the viscosified treatment fluids
US20050059558A1 (en) * 2003-06-27 2005-03-17 Blauch Matthew E. Methods for improving proppant pack permeability and fracture conductivity in a subterranean well
US20050056423A1 (en) * 2003-09-11 2005-03-17 Todd Bradey L. Methods of removing filter cake from well producing zones
US20050059556A1 (en) * 2003-09-17 2005-03-17 Trinidad Munoz Treatment fluids and methods of use in subterranean formations
US20050126780A1 (en) * 2003-06-27 2005-06-16 Halliburton Energy Services, Inc. Compositions and methods for improving fracture conductivity in a subterranean well
US20050126785A1 (en) * 2003-12-15 2005-06-16 Todd Bradley L. Filter cake degradation compositions and methods of use in subterranean operations
US20050161220A1 (en) * 2004-01-27 2005-07-28 Todd Bradley L. Fluid loss control additives for use in fracturing subterranean formations
US20050167105A1 (en) * 2004-01-30 2005-08-04 Roddy Craig W. Contained micro-particles for use in well bore operations
US20050167104A1 (en) * 2004-01-30 2005-08-04 Roddy Craig W. Compositions and methods for the delivery of chemical components in subterranean well bores
US20050167107A1 (en) * 2004-01-30 2005-08-04 Roddy Craig W. Methods of cementing in subterranean formations using crack resistant cement compositions
US20050183329A1 (en) * 2004-02-16 2005-08-25 Cederblad Hans O. Biodegradable netting
US20050205258A1 (en) * 2004-03-17 2005-09-22 Reddy B R Cement compositions containing degradable materials and methods of cementing in subterranean formations
US6997259B2 (en) 2003-09-05 2006-02-14 Halliburton Energy Services, Inc. Methods for forming a permeable and stable mass in a subterranean formation
US20060048938A1 (en) * 2004-09-03 2006-03-09 Kalman Mark D Carbon foam particulates and methods of using carbon foam particulates in subterranean applications
US7070795B1 (en) 1997-06-30 2006-07-04 Monsanto Company Particles containing agricultural active ingredients
US20060169453A1 (en) * 2005-02-01 2006-08-03 Savery Mark R Kickoff plugs comprising a self-degrading cement in subterranean well bores
US20060169449A1 (en) * 2005-01-31 2006-08-03 Halliburton Energy Services, Inc. Self-degrading fibers and associated methods of use and manufacture
US20060185847A1 (en) * 2005-02-22 2006-08-24 Halliburton Energy Services, Inc. Methods of placing treatment chemicals
US7237610B1 (en) 2006-03-30 2007-07-03 Halliburton Energy Services, Inc. Degradable particulates as friction reducers for the flow of solid particulates and associated methods of use
US20070289781A1 (en) * 2006-02-10 2007-12-20 Halliburton Energy Services, Inc. Consolidating agent emulsions and associated methods
US20080006406A1 (en) * 2006-07-06 2008-01-10 Halliburton Energy Services, Inc. Methods of enhancing uniform placement of a resin in a subterranean formation
US20080076696A1 (en) * 2006-06-21 2008-03-27 David Uitenbrock Dryer sheet and methods for manufacturing and using a dryer sheet
US20080076314A1 (en) * 2006-09-26 2008-03-27 John James Blanz Wipe and methods for manufacturing and using a wipe
US20080076313A1 (en) * 2006-09-26 2008-03-27 David Uitenbroek Wipe and methods for manufacturing and using a wipe
US20080076695A1 (en) * 2006-09-26 2008-03-27 David Uitenbroek Dryer sheet and methods for manufacturing and using a dryer sheet
US20080102272A1 (en) * 2006-09-21 2008-05-01 Yuichiro Sakamoto Adhesive wrapping film
US7413017B2 (en) 2004-09-24 2008-08-19 Halliburton Energy Services, Inc. Methods and compositions for inducing tip screenouts in frac-packing operations
US20080268018A1 (en) * 2007-04-30 2008-10-30 Pacetti Stephen D Method for forming crystallized therapeutic agents on a medical device
US20080311320A1 (en) * 2005-11-30 2008-12-18 Mitsubishi Plastics , Inc. Polyolefin Series Heat-Shrinkable Film, Molded Product and Heat-Shrinkable Laminated Label Employing the Film, and Container
US7475728B2 (en) 2004-07-23 2009-01-13 Halliburton Energy Services, Inc. Treatment fluids and methods of use in subterranean formations
US7497278B2 (en) 2003-08-14 2009-03-03 Halliburton Energy Services, Inc. Methods of degrading filter cakes in a subterranean formation
US20090074999A1 (en) * 2005-05-11 2009-03-19 Takashi Hiruma Heat-shrinkable film, moldings and heat-shrinkable labels made using the heat-shrinkable film, and containers made by using the moldings or fitted with the labels
US7506689B2 (en) 2005-02-22 2009-03-24 Halliburton Energy Services, Inc. Fracturing fluids comprising degradable diverting agents and methods of use in subterranean formations
US7553800B2 (en) 2004-11-17 2009-06-30 Halliburton Energy Services, Inc. In-situ filter cake degradation compositions and methods of use in subterranean formations
US7608566B2 (en) 2006-03-30 2009-10-27 Halliburton Energy Services, Inc. Degradable particulates as friction reducers for the flow of solid particulates and associated methods of use
US20090311544A1 (en) * 2008-06-13 2009-12-17 Toray Plastics (America), Inc. Method to produce matte and opaque biaxially oriented polylactic acid film
US7648946B2 (en) 2004-11-17 2010-01-19 Halliburton Energy Services, Inc. Methods of degrading filter cakes in subterranean formations
US7662753B2 (en) 2005-05-12 2010-02-16 Halliburton Energy Services, Inc. Degradable surfactants and methods for use
US7665517B2 (en) 2006-02-15 2010-02-23 Halliburton Energy Services, Inc. Methods of cleaning sand control screens and gravel packs
US7674753B2 (en) 2003-09-17 2010-03-09 Halliburton Energy Services, Inc. Treatment fluids and methods of forming degradable filter cakes comprising aliphatic polyester and their use in subterranean formations
US7673686B2 (en) 2005-03-29 2010-03-09 Halliburton Energy Services, Inc. Method of stabilizing unconsolidated formation for sand control
US7678742B2 (en) 2006-09-20 2010-03-16 Halliburton Energy Services, Inc. Drill-in fluids and associated methods
US7678743B2 (en) 2006-09-20 2010-03-16 Halliburton Energy Services, Inc. Drill-in fluids and associated methods
US7677315B2 (en) 2005-05-12 2010-03-16 Halliburton Energy Services, Inc. Degradable surfactants and methods for use
US7686080B2 (en) 2006-11-09 2010-03-30 Halliburton Energy Services, Inc. Acid-generating fluid loss control additives and associated methods
US7687438B2 (en) 2006-09-20 2010-03-30 Halliburton Energy Services, Inc. Drill-in fluids and associated methods
US7700525B2 (en) 2005-09-22 2010-04-20 Halliburton Energy Services, Inc. Orthoester-based surfactants and associated methods
US7712531B2 (en) 2004-06-08 2010-05-11 Halliburton Energy Services, Inc. Methods for controlling particulate migration
US20100126685A1 (en) * 2008-11-25 2010-05-27 Dixie Consumer Products Llc Paper Products
US7757768B2 (en) 2004-10-08 2010-07-20 Halliburton Energy Services, Inc. Method and composition for enhancing coverage and displacement of treatment fluids into subterranean formations
WO2010105142A1 (en) 2009-03-13 2010-09-16 Natureworks Llc Recovery of lactic acid values from a meso-lactide stream
WO2010105143A2 (en) 2009-03-13 2010-09-16 Natureworks Llc Methods for producing lactide with recycle of meso-lactide
US7833944B2 (en) 2003-09-17 2010-11-16 Halliburton Energy Services, Inc. Methods and compositions using crosslinked aliphatic polyesters in well bore applications
US7833943B2 (en) 2008-09-26 2010-11-16 Halliburton Energy Services Inc. Microemulsifiers and methods of making and using same
US7883740B2 (en) 2004-12-12 2011-02-08 Halliburton Energy Services, Inc. Low-quality particulates and methods of making and using improved low-quality particulates
US7906464B2 (en) 2008-05-13 2011-03-15 Halliburton Energy Services, Inc. Compositions and methods for the removal of oil-based filtercakes
US7926591B2 (en) 2006-02-10 2011-04-19 Halliburton Energy Services, Inc. Aqueous-based emulsified consolidating agents suitable for use in drill-in applications
US7963330B2 (en) 2004-02-10 2011-06-21 Halliburton Energy Services, Inc. Resin compositions and methods of using resin compositions to control proppant flow-back
US7998910B2 (en) 2009-02-24 2011-08-16 Halliburton Energy Services, Inc. Treatment fluids comprising relative permeability modifiers and methods of use
US8006760B2 (en) 2008-04-10 2011-08-30 Halliburton Energy Services, Inc. Clean fluid systems for partial monolayer fracturing
US8017561B2 (en) 2004-03-03 2011-09-13 Halliburton Energy Services, Inc. Resin compositions and methods of using such resin compositions in subterranean applications
US20110230599A1 (en) * 2010-03-16 2011-09-22 Michael James Deaner Sustainable Compositions, Related Methods, and Members Formed Therefrom
US8030251B2 (en) 2005-01-28 2011-10-04 Halliburton Energy Services, Inc. Methods and compositions relating to the hydrolysis of water-hydrolysable materials
US8030249B2 (en) 2005-01-28 2011-10-04 Halliburton Energy Services, Inc. Methods and compositions relating to the hydrolysis of water-hydrolysable materials
US8082992B2 (en) 2009-07-13 2011-12-27 Halliburton Energy Services, Inc. Methods of fluid-controlled geometry stimulation
US8188013B2 (en) 2005-01-31 2012-05-29 Halliburton Energy Services, Inc. Self-degrading fibers and associated methods of use and manufacture
US8220548B2 (en) 2007-01-12 2012-07-17 Halliburton Energy Services Inc. Surfactant wash treatment fluids and associated methods
US8329621B2 (en) 2006-07-25 2012-12-11 Halliburton Energy Services, Inc. Degradable particulates and associated methods
US8354279B2 (en) 2002-04-18 2013-01-15 Halliburton Energy Services, Inc. Methods of tracking fluids produced from various zones in a subterranean well
US8541051B2 (en) 2003-08-14 2013-09-24 Halliburton Energy Services, Inc. On-the fly coating of acid-releasing degradable material onto a particulate
WO2013166469A2 (en) 2012-05-03 2013-11-07 Virdia Ltd Methods for treating lignocellulosic materials
US8598092B2 (en) 2005-02-02 2013-12-03 Halliburton Energy Services, Inc. Methods of preparing degradable materials and methods of use in subterranean formations
US8613320B2 (en) 2006-02-10 2013-12-24 Halliburton Energy Services, Inc. Compositions and applications of resins in treating subterranean formations
US8689872B2 (en) 2005-07-11 2014-04-08 Halliburton Energy Services, Inc. Methods and compositions for controlling formation fines and reducing proppant flow-back
US8829097B2 (en) 2012-02-17 2014-09-09 Andersen Corporation PLA-containing material
US9035076B2 (en) 2009-03-13 2015-05-19 Natureworks Llc Recovery of lactic acid values from a meso-lactide stream
US9173973B2 (en) 2006-07-20 2015-11-03 G. Lawrence Thatcher Bioabsorbable polymeric composition for a medical device
US9211205B2 (en) 2006-10-20 2015-12-15 Orbusneich Medical, Inc. Bioabsorbable medical device with coating
US9334518B2 (en) 2013-03-08 2016-05-10 Xyleco, Inc. Array for processing materials
US9493851B2 (en) 2012-05-03 2016-11-15 Virdia, Inc. Methods for treating lignocellulosic materials
US9724864B2 (en) 2006-10-20 2017-08-08 Orbusneich Medical, Inc. Bioabsorbable polymeric composition and medical device
US20170313912A1 (en) * 2014-12-22 2017-11-02 3M Innovative Properties Company Compositions and films comprising polylactic acid polymer, polyvinyl acetate polymer and plasticizer
EP3406605A1 (en) 2017-05-22 2018-11-28 NatureWorks LLC Methods for producing lactide with recrystallization and recycle of meso-lactide
US10876178B2 (en) 2011-04-07 2020-12-29 Virdia, Inc. Lignocellulosic conversion processes and products
US10982090B2 (en) 2016-06-21 2021-04-20 3M Innovative Properties Company Graphic articles comprising polylactic acid polymer based film
US11066551B2 (en) 2016-05-20 2021-07-20 3M Innovative Properties Company Oriented polylactic acid polymer based film

Families Citing this family (334)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6740731B2 (en) * 1988-08-08 2004-05-25 Cargill Dow Polymers Llc Degradation control of environmentally degradable disposable materials
US5444113A (en) * 1988-08-08 1995-08-22 Ecopol, Llc End use applications of biodegradable polymers
US6005068A (en) 1992-10-02 1999-12-21 Cargill Incorporated Melt-stable amorphous lactide polymer film and process for manufacture thereof
ATE199944T1 (en) * 1992-10-02 2001-04-15 Cargill Inc MELT-STABLE LACTIDE POLYMER FABRIC AND METHOD FOR THE PRODUCTION THEREOF
DE69322155T2 (en) * 1992-10-02 1999-08-19 Cargill Inc PAPER WITH A COATING FROM MELT-STABLE POLYMER AND ITS METHOD FOR THE PRODUCTION THEREOF
US5359026A (en) * 1993-07-30 1994-10-25 Cargill, Incorporated Poly(lactide) copolymer and process for manufacture thereof
US6017661A (en) 1994-11-09 2000-01-25 Kimberly-Clark Corporation Temporary marking using photoerasable colorants
US5681380A (en) 1995-06-05 1997-10-28 Kimberly-Clark Worldwide, Inc. Ink for ink jet printers
US5865471A (en) 1993-08-05 1999-02-02 Kimberly-Clark Worldwide, Inc. Photo-erasable data processing forms
US6017471A (en) 1993-08-05 2000-01-25 Kimberly-Clark Worldwide, Inc. Colorants and colorant modifiers
US5773182A (en) 1993-08-05 1998-06-30 Kimberly-Clark Worldwide, Inc. Method of light stabilizing a colorant
US5645964A (en) 1993-08-05 1997-07-08 Kimberly-Clark Corporation Digital information recording media and method of using same
US6211383B1 (en) 1993-08-05 2001-04-03 Kimberly-Clark Worldwide, Inc. Nohr-McDonald elimination reaction
US5733693A (en) 1993-08-05 1998-03-31 Kimberly-Clark Worldwide, Inc. Method for improving the readability of data processing forms
US5721287A (en) 1993-08-05 1998-02-24 Kimberly-Clark Worldwide, Inc. Method of mutating a colorant by irradiation
BR9408383A (en) * 1993-12-20 1997-08-26 Procter & Gamble Polymer composition endowed with increased biodegradability in the process film to increase the biodegradability of a polymer and absorbent article
FI99125C (en) 1993-12-31 1997-10-10 Neste Oy Polylaktidsammansättning
JPH07205278A (en) * 1994-01-11 1995-08-08 Mitsubishi Plastics Ind Ltd Production of stretched film of polylactic acid polymer
JP3330712B2 (en) * 1994-01-11 2002-09-30 三菱樹脂株式会社 Method for producing polylactic acid-based film
DE69509927T2 (en) * 1994-01-21 2000-01-27 Shimadzu Corp Method of producing polylactic acid
US5639466A (en) * 1994-02-24 1997-06-17 Chronopol, Inc. Method for packaging foodstuffs
JP3328418B2 (en) * 1994-03-28 2002-09-24 三菱樹脂株式会社 Heat-shrinkable polylactic acid film
US6242057B1 (en) 1994-06-30 2001-06-05 Kimberly-Clark Worldwide, Inc. Photoreactor composition and applications therefor
US5685754A (en) 1994-06-30 1997-11-11 Kimberly-Clark Corporation Method of generating a reactive species and polymer coating applications therefor
US6071979A (en) 1994-06-30 2000-06-06 Kimberly-Clark Worldwide, Inc. Photoreactor composition method of generating a reactive species and applications therefor
US6008268A (en) 1994-10-21 1999-12-28 Kimberly-Clark Worldwide, Inc. Photoreactor composition, method of generating a reactive species, and applications therefor
JP2688330B2 (en) * 1994-10-25 1997-12-10 株式会社日本触媒 Polyester resin composition
JP3022226B2 (en) * 1994-12-08 2000-03-15 大伸化学株式会社 Catalytic method in electroless plating
US5714573A (en) 1995-01-19 1998-02-03 Cargill, Incorporated Impact modified melt-stable lactide polymer compositions and processes for manufacture thereof
US5786132A (en) 1995-06-05 1998-07-28 Kimberly-Clark Corporation Pre-dyes, mutable dye compositions, and methods of developing a color
JP2001515524A (en) 1995-06-05 2001-09-18 キンバリー クラーク ワールドワイド インコーポレイテッド New pre-dye
AU5535296A (en) 1995-06-28 1997-01-30 Kimberly-Clark Worldwide, Inc. Novel colorants and colorant modifiers
CN1149596A (en) * 1995-08-23 1997-05-14 联合碳化化学品及塑料技术公司 Stable dioxaneone polymer
US5675022A (en) * 1995-08-23 1997-10-07 Union Carbide Chemicals & Plastics Technology Corporation Recovery of dioxanone by melt crystallization
JP3482748B2 (en) * 1995-09-11 2004-01-06 大日本インキ化学工業株式会社 Method for producing lactic acid-based polyester
US5686540A (en) * 1995-09-29 1997-11-11 Dainippon Ink And Chemicals, Inc. Process for the preparation of lactic acid-based polyester
ES2175168T3 (en) 1995-11-28 2002-11-16 Kimberly Clark Co COLOR COMPOUNDS STABILIZED BY LIGHT.
US5782963A (en) 1996-03-29 1998-07-21 Kimberly-Clark Worldwide, Inc. Colorant stabilizers
US6099628A (en) 1996-03-29 2000-08-08 Kimberly-Clark Worldwide, Inc. Colorant stabilizers
US5855655A (en) 1996-03-29 1999-01-05 Kimberly-Clark Worldwide, Inc. Colorant stabilizers
US5891229A (en) 1996-03-29 1999-04-06 Kimberly-Clark Worldwide, Inc. Colorant stabilizers
JP3951144B2 (en) * 1996-06-26 2007-08-01 チバ スペシャルティ ケミカルズ ホールディング インコーポレーテッド Polymer degradation using NOR-HALS compounds
US5851937A (en) * 1997-03-27 1998-12-22 Clopay Plastic Products Company, Inc. Cloth-like totally biodegradable and/or compostable composites and method of manufacture
FI980086A (en) 1997-05-28 1998-11-29 Enso Oyj Coated paperboard, its method of manufacture and containers and packaging made from it
US6524379B2 (en) 1997-08-15 2003-02-25 Kimberly-Clark Worldwide, Inc. Colorants, colorant stabilizers, ink compositions, and improved methods of making the same
US6089009A (en) 1997-08-28 2000-07-18 Belmont Textile Machinery Co., Inc. Fluid-jet false-twisting method and product
US6268434B1 (en) 1997-10-31 2001-07-31 Kimberly Clark Worldwide, Inc. Biodegradable polylactide nonwovens with improved fluid management properties
US6201068B1 (en) 1997-10-31 2001-03-13 Kimberly-Clark Worldwide, Inc. Biodegradable polylactide nonwovens with improved fluid management properties
US6306782B1 (en) 1997-12-22 2001-10-23 Kimberly-Clark Worldwide, Inc. Disposable absorbent product having biodisintegratable nonwovens with improved fluid management properties
US6544455B1 (en) 1997-12-22 2003-04-08 Kimberly-Clark Worldwide, Inc. Methods for making a biodegradable thermoplastic composition
US6309988B1 (en) 1997-12-22 2001-10-30 Kimberly-Clark Worldwide, Inc. Biodisintegratable nonwovens with improved fluid management properties
US6372850B2 (en) 1997-12-31 2002-04-16 Kimberly-Clark Worldwide, Inc. Melt processable poly (ethylene oxide) fibers
US6164011A (en) * 1998-02-02 2000-12-26 Cascades Multi-Pro Inc. Biodegradable and biocompatible agricultural mulch and method of preparing same
JP4543271B2 (en) * 1998-05-28 2010-09-15 グンゼ株式会社 Lactide-containing polymers and medical materials
EP1062285A2 (en) 1998-06-03 2000-12-27 Kimberly-Clark Worldwide, Inc. Neonanoplasts and microemulsion technology for inks and ink jet printing
CA2298468A1 (en) 1998-06-03 1999-12-09 John Gavin Macdonald Novel photoinitiators and applications therefor
WO2000004104A1 (en) 1998-07-20 2000-01-27 Kimberly-Clark Worldwide, Inc. Improved ink jet ink compositions
JP2987580B1 (en) * 1998-08-07 1999-12-06 西川ゴム工業株式会社 Biodegradable resin and method for producing the same
US6197860B1 (en) 1998-08-31 2001-03-06 Kimberly-Clark Worldwide, Inc. Biodegradable nonwovens with improved fluid management properties
US6194483B1 (en) 1998-08-31 2001-02-27 Kimberly-Clark Worldwide, Inc. Disposable articles having biodegradable nonwovens with improved fluid management properties
JP2000095898A (en) * 1998-09-24 2000-04-04 Jsr Corp Biodegradable material modifier, and biodegradable material composition using the same
AU1309800A (en) 1998-09-28 2000-04-17 Kimberly-Clark Worldwide, Inc. Novel photoinitiators and applications therefor
US20030199218A1 (en) * 1998-10-23 2003-10-23 Mueller Louann S. Ream wrap comprising PLA resin
US20030129431A1 (en) * 1998-10-23 2003-07-10 Michael R. Nowak Composite wrap material
DE60002294T2 (en) 1999-01-19 2003-10-30 Kimberly Clark Co DYES, COLOR STABILIZERS, INK COMPOSITIONS AND METHOD FOR THE PRODUCTION THEREOF
US6331056B1 (en) 1999-02-25 2001-12-18 Kimberly-Clark Worldwide, Inc. Printing apparatus and applications therefor
US6342065B1 (en) * 1999-03-17 2002-01-29 Poly-Med, Inc. High strength fibers of L-lactide copolymers ε-caprolactone and trimethylene carbonate and absorbable medical constructs thereof
US6608170B1 (en) * 1999-03-31 2003-08-19 Cornell Research Foundation, Inc. Syndiotactic poly(lactic acid)
US6294698B1 (en) 1999-04-16 2001-09-25 Kimberly-Clark Worldwide, Inc. Photoinitiators and applications therefor
US6217630B1 (en) 1999-05-03 2001-04-17 Cargill, Incorporated Conditioned fertilizer product, method for conditioning fertilizer, and method for using conditioned fertilizer product
US6368395B1 (en) 1999-05-24 2002-04-09 Kimberly-Clark Worldwide, Inc. Subphthalocyanine colorants, ink compositions, and method of making the same
US6576246B1 (en) * 1999-05-24 2003-06-10 Seefar Technologies, Inc. Degradable animal chewing article possessing enhanced safety, durability and mouth-feel
WO2001000730A1 (en) * 1999-06-25 2001-01-04 Mitsui Chemicals, Inc. Aliphatic polyester composition for masterbatch and process for producing aliphatic polyester film with the composition
KR20010086308A (en) * 2000-01-14 2001-09-10 임현덕 Injection molding composition comprising paper and method for preparing the same
US20030121630A1 (en) * 2000-04-19 2003-07-03 Zhirun Yuan Inhibition of yellowing in papers
JP4296695B2 (en) * 2000-07-19 2009-07-15 セイコーエプソン株式会社 Pulp molded product and method for producing the same
WO2002051284A2 (en) * 2000-12-26 2002-07-04 Avon Products, Inc. Applicator brushes and method for using same
JP2002210886A (en) * 2001-01-19 2002-07-31 Toray Ind Inc Softened biodegradable resin stretched film
US20050274322A1 (en) * 2001-02-26 2005-12-15 Lee Chung J Reactor for producing reactive intermediates for low dielectric constant polymer thin films
US20040255862A1 (en) * 2001-02-26 2004-12-23 Lee Chung J. Reactor for producing reactive intermediates for low dielectric constant polymer thin films
DE10113302B4 (en) * 2001-03-19 2009-09-24 Fraunhofer-Gesellschaft für die angewandte Forschung e.V. Process for the preparation of homo- and copolyesters of lactic acid
US6905759B2 (en) * 2001-04-23 2005-06-14 Kimberly Clark Worldwide, Inc. Biodegradable films having enhanced ductility and breathability
US6660211B2 (en) 2001-04-23 2003-12-09 Kimberly-Clark Worldwide, Inc. Methods of making biodegradable films having enhanced ductility and breathability
US6645618B2 (en) 2001-06-15 2003-11-11 3M Innovative Properties Company Aliphatic polyester microfibers, microfibrillated articles and use thereof
EP1281724B1 (en) * 2001-08-01 2006-01-11 Fuji Photo Film Co., Ltd. Biodegrable resin molded article and production method thereof
US6616748B2 (en) 2001-08-03 2003-09-09 Zo Resources, Llc High performance purified natural zeolite pigment for papermaking and paper coating
WO2003016015A1 (en) * 2001-08-20 2003-02-27 Cargill Dow Llc Method for producing semicrystalline polylactic acid articles
ES2295451T3 (en) * 2001-09-28 2008-04-16 Basf Se SOLID BIODEGRADABLE PREPARATION OF A PESTICIDE WITH DELAYED RELEASE OF ACTIVE PRINCIPLES.
US20030091760A1 (en) * 2001-11-09 2003-05-15 Cecile Drogou Adhesive for difficult to bond substrates
WO2003046790A1 (en) * 2001-11-27 2003-06-05 Accenture Llp Context sensitive advertisement delivery framework
US6962200B2 (en) * 2002-01-08 2005-11-08 Halliburton Energy Services, Inc. Methods and compositions for consolidating proppant in subterranean fractures
US7216711B2 (en) * 2002-01-08 2007-05-15 Halliburton Eenrgy Services, Inc. Methods of coating resin and blending resin-coated proppant
US7267171B2 (en) * 2002-01-08 2007-09-11 Halliburton Energy Services, Inc. Methods and compositions for stabilizing the surface of a subterranean formation
US7343973B2 (en) * 2002-01-08 2008-03-18 Halliburton Energy Services, Inc. Methods of stabilizing surfaces of subterranean formations
JP2003240955A (en) * 2002-02-21 2003-08-27 Konica Corp Optical film, polarizing plate, optical film roll, display device using optical film and method for manufacturing optical film
JP4199572B2 (en) * 2002-03-29 2008-12-17 三井化学株式会社 Lactic acid resin composition
JP4179585B2 (en) * 2002-03-29 2008-11-12 ユニ・チャーム株式会社 Printed biodegradable plastic film
DE10216834A1 (en) * 2002-04-16 2003-11-13 Fraunhofer Ges Forschung Process for producing melt-stable homo- and copolyesters of cyclic esters and / or diesters
JP4084953B2 (en) 2002-04-18 2008-04-30 日清紡績株式会社 Biodegradable plastic composition, molded product thereof, and biodegradation rate control method
US6890649B2 (en) 2002-04-26 2005-05-10 3M Innovative Properties Company Aliphatic polyester microfibers, microfibrillated articles and use thereof
US7348052B2 (en) * 2002-05-07 2008-03-25 Coating Excellence International Sandwich wrappers, fast food wrappers, and gum wrappers comprising PLA resin
BR0311453A (en) 2002-05-30 2005-03-29 Cargill Dow Llc Methods and materials for the production of d-lactic acid in yeast
JP2003002984A (en) * 2002-06-14 2003-01-08 Mitsubishi Plastics Ind Ltd Polylactic acid film
JP3742842B2 (en) * 2002-06-17 2006-02-08 独立行政法人産業技術総合研究所 Biodegradable polylactic acid resin composition
AU2003248270A1 (en) * 2002-07-11 2004-02-02 Mitsubishi Plastics, Inc. Biodegradable laminate sheet and molded item from biodegradable laminate sheet
US20040024102A1 (en) * 2002-07-30 2004-02-05 Hayes Richard Allen Sulfonated aliphatic-aromatic polyetherester films, coatings, and laminates
MXPA05001148A (en) * 2002-07-31 2005-11-23 Macropore Biosurgery Inc Resorbable thin membranes.
CN101057824A (en) * 2002-07-31 2007-10-24 阿尔萨公司 Injectable multimodal polymer depot compositions and uses thereof
US7670545B2 (en) * 2002-08-19 2010-03-02 Natureworks Llc Method for producing semicrystalline polylactic acid articles
US6705400B1 (en) * 2002-08-28 2004-03-16 Halliburton Energy Services, Inc. Methods and compositions for forming subterranean fractures containing resilient proppant packs
KR101054241B1 (en) * 2002-09-09 2011-08-08 소니 주식회사 Resin composition
JP4245333B2 (en) * 2002-11-08 2009-03-25 日清紡績株式会社 Biodegradable plastic composition, molded product thereof, and biodegradation rate control method using the same
US7303642B2 (en) * 2002-11-12 2007-12-04 Kimberly-Clark Worldwide, Inc. Methods of making responsive film with corrugated microlayers having improved properties
US6984439B2 (en) * 2002-11-12 2006-01-10 Kimberly-Clark Worldwide, Inc. Responsive film with corrugated microlayers having improved properties
US7994078B2 (en) * 2002-12-23 2011-08-09 Kimberly-Clark Worldwide, Inc. High strength nonwoven web from a biodegradable aliphatic polyester
US7700500B2 (en) * 2002-12-23 2010-04-20 Kimberly-Clark Worldwide, Inc. Durable hydrophilic treatment for a biodegradable polymeric substrate
US20040211561A1 (en) * 2003-03-06 2004-10-28 Nguyen Philip D. Methods and compositions for consolidating proppant in fractures
US7114570B2 (en) * 2003-04-07 2006-10-03 Halliburton Energy Services, Inc. Methods and compositions for stabilizing unconsolidated subterranean formations
CN1320044C (en) 2003-04-25 2007-06-06 株式会社艾迪科 Polylactic acids compsns. make-up products and prepn. process thereof
US20050009687A1 (en) * 2003-05-02 2005-01-13 Verkade John G. Titanium alkoxide catalysts for polymerization of cyclic esters and methods of polymerization
JP3889376B2 (en) * 2003-05-16 2007-03-07 松下電器産業株式会社 Battery package and manufacturing method thereof
US6978836B2 (en) * 2003-05-23 2005-12-27 Halliburton Energy Services, Inc. Methods for controlling water and particulate production
US7114560B2 (en) * 2003-06-23 2006-10-03 Halliburton Energy Services, Inc. Methods for enhancing treatment fluid placement in a subterranean formation
US7413010B2 (en) * 2003-06-23 2008-08-19 Halliburton Energy Services, Inc. Remediation of subterranean formations using vibrational waves and consolidating agents
US20050130848A1 (en) * 2003-06-27 2005-06-16 Halliburton Energy Services, Inc. Compositions and methods for improving fracture conductivity in a subterranean well
US7021379B2 (en) * 2003-07-07 2006-04-04 Halliburton Energy Services, Inc. Methods and compositions for enhancing consolidation strength of proppant in subterranean fractures
US7104325B2 (en) * 2003-07-09 2006-09-12 Halliburton Energy Services, Inc. Methods of consolidating subterranean zones and compositions therefor
US7179952B2 (en) * 2003-08-25 2007-02-20 Kimberly-Clark Worldwide, Inc. Absorbent article formed with microlayered films
US7017665B2 (en) * 2003-08-26 2006-03-28 Halliburton Energy Services, Inc. Strengthening near well bore subterranean formations
US7059406B2 (en) * 2003-08-26 2006-06-13 Halliburton Energy Services, Inc. Production-enhancing completion methods
US7156194B2 (en) * 2003-08-26 2007-01-02 Halliburton Energy Services, Inc. Methods of drilling and consolidating subterranean formation particulate
US7237609B2 (en) * 2003-08-26 2007-07-03 Halliburton Energy Services, Inc. Methods for producing fluids from acidized and consolidated portions of subterranean formations
US7032667B2 (en) * 2003-09-10 2006-04-25 Halliburtonn Energy Services, Inc. Methods for enhancing the consolidation strength of resin coated particulates
US7345011B2 (en) * 2003-10-14 2008-03-18 Halliburton Energy Services, Inc. Methods for mitigating the production of water from subterranean formations
US20050089631A1 (en) * 2003-10-22 2005-04-28 Nguyen Philip D. Methods for reducing particulate density and methods of using reduced-density particulates
EP1679183A4 (en) * 2003-10-27 2008-11-05 Mitsubishi Plastics Inc Reflective film
US7063150B2 (en) * 2003-11-25 2006-06-20 Halliburton Energy Services, Inc. Methods for preparing slurries of coated particulates
US20050136155A1 (en) * 2003-12-22 2005-06-23 Jordan Joy F. Specialty beverage infusion package
US20050145385A1 (en) * 2004-01-05 2005-07-07 Nguyen Philip D. Methods of well stimulation and completion
US20070007009A1 (en) * 2004-01-05 2007-01-11 Halliburton Energy Services, Inc. Methods of well stimulation and completion
US7131493B2 (en) * 2004-01-16 2006-11-07 Halliburton Energy Services, Inc. Methods of using sealants in multilateral junctions
US7888405B2 (en) 2004-01-30 2011-02-15 E. I. Du Pont De Nemours And Company Aliphatic-aromatic polyesters, and articles made therefrom
US7393590B2 (en) * 2004-02-27 2008-07-01 Cereplast, Inc. Biodegradable poly(lactic acid) polymer composition and films, coatings and products comprising Biodegradable poly(lactic acid) polymer compositions
US20050194142A1 (en) * 2004-03-05 2005-09-08 Nguyen Philip D. Compositions and methods for controlling unconsolidated particulates
US7063151B2 (en) * 2004-03-05 2006-06-20 Halliburton Energy Services, Inc. Methods of preparing and using coated particulates
JP4243292B2 (en) * 2004-03-16 2009-03-25 帝人株式会社 Ultra-fine polylactic acid fiber, fiber structure, and production method thereof
FR2867698B1 (en) 2004-03-16 2007-11-16 Beaufour Ipsen S C R A S CATALYTIC SYSTEM FOR (CO) OLIGOMERIZATION OF LACTIDE AND GLYCOLIDE
JP4498783B2 (en) * 2004-03-17 2010-07-07 トヨタ紡織株式会社 Method for producing wooden molded body
US6962871B2 (en) * 2004-03-31 2005-11-08 Dielectric Systems, Inc. Composite polymer dielectric film
US7094661B2 (en) * 2004-03-31 2006-08-22 Dielectric Systems, Inc. Single and dual damascene techniques utilizing composite polymer dielectric film
US7309395B2 (en) 2004-03-31 2007-12-18 Dielectric Systems, Inc. System for forming composite polymer dielectric film
PL1732756T3 (en) * 2004-04-05 2011-04-29 Leucadia Inc Degradable netting
US20070078063A1 (en) * 2004-04-26 2007-04-05 Halliburton Energy Services, Inc. Subterranean treatment fluids and methods of treating subterranean formations
US8513379B2 (en) 2004-04-28 2013-08-20 Keio University Depolymerization method for polymer containing ester bond in main chain and method for producing polymer containing ester bond in main chain from depolymerization product
US20050250931A1 (en) * 2004-05-05 2005-11-10 Mitsubishi Plastics, Inc. Shredder dust for recycling, molding for shredder dust and a method for recovering lactide from the shredder dust as well as molding formed from the lactide
CA2569099C (en) * 2004-05-07 2011-07-12 Marc S. Theisen Composite fiber environmental filtration media containing flocculant
US20050263283A1 (en) * 2004-05-25 2005-12-01 Nguyen Philip D Methods for stabilizing and stimulating wells in unconsolidated subterranean formations
US20060201426A1 (en) * 2004-05-25 2006-09-14 Lee Chung J Reactor for Producing Reactive Intermediates for Transport Polymerization
US7541318B2 (en) * 2004-05-26 2009-06-02 Halliburton Energy Services, Inc. On-the-fly preparation of proppant and its use in subterranean operations
US7073581B2 (en) * 2004-06-15 2006-07-11 Halliburton Energy Services, Inc. Electroconductive proppant compositions and related methods
JP2006001574A (en) * 2004-06-16 2006-01-05 Matsushita Electric Ind Co Ltd Battery package and its manufacturing method
US7358325B2 (en) * 2004-07-09 2008-04-15 E. I. Du Pont De Nemours And Company Sulfonated aromatic copolyesters containing hydroxyalkanoic acid groups and shaped articles produced therefrom
US7193029B2 (en) * 2004-07-09 2007-03-20 E. I. Du Pont De Nemours And Company Sulfonated copolyetherester compositions from hydroxyalkanoic acids and shaped articles produced therefrom
US7144972B2 (en) * 2004-07-09 2006-12-05 E. I. Du Pont De Nemours And Company Copolyetherester compositions containing hydroxyalkanoic acids and shaped articles produced therefrom
US7547665B2 (en) 2005-04-29 2009-06-16 Halliburton Energy Services, Inc. Acidic treatment fluids comprising scleroglucan and/or diutan and associated methods
US7621334B2 (en) 2005-04-29 2009-11-24 Halliburton Energy Services, Inc. Acidic treatment fluids comprising scleroglucan and/or diutan and associated methods
US8980300B2 (en) * 2004-08-05 2015-03-17 Advanced Cardiovascular Systems, Inc. Plasticizers for coating compositions
US20060032633A1 (en) * 2004-08-10 2006-02-16 Nguyen Philip D Methods and compositions for carrier fluids comprising water-absorbent fibers
US20060046044A1 (en) * 2004-08-24 2006-03-02 Lee Chung J Porous composite polymer dielectric film
US8133558B2 (en) * 2004-08-30 2012-03-13 Plastics Suppliers, Inc. Polylactic acid blown film and method of manufacturing same
US20060046938A1 (en) * 2004-09-02 2006-03-02 Harris Philip C Methods and compositions for delinking crosslinked fluids
JP4640765B2 (en) 2004-09-03 2011-03-02 株式会社Adeka Polylactic acid-based resin composition, molded article and method for producing the same
US7281580B2 (en) * 2004-09-09 2007-10-16 Halliburton Energy Services, Inc. High porosity fractures and methods of creating high porosity fractures
US7404999B2 (en) * 2004-09-30 2008-07-29 Graphic Packaging International, Inc. Anti-blocking barrier composite
US7416767B2 (en) * 2004-09-30 2008-08-26 Graphic Packaging International, Inc. Anti-blocking coatings for PVdc-coated substrates
JP2006143932A (en) * 2004-11-22 2006-06-08 Mitsubishi Chemicals Corp Aliphatic or alicyclic polyester resin composition
US7281581B2 (en) * 2004-12-01 2007-10-16 Halliburton Energy Services, Inc. Methods of hydraulic fracturing and of propping fractures in subterranean formations
US7273099B2 (en) * 2004-12-03 2007-09-25 Halliburton Energy Services, Inc. Methods of stimulating a subterranean formation comprising multiple production intervals
US7398825B2 (en) * 2004-12-03 2008-07-15 Halliburton Energy Services, Inc. Methods of controlling sand and water production in subterranean zones
ES2387927T3 (en) 2004-12-17 2012-10-04 Devgen Nv Nematicidal compositions
US20060159918A1 (en) * 2004-12-22 2006-07-20 Fiber Innovation Technology, Inc. Biodegradable fibers exhibiting storage-stable tenacity
US7334635B2 (en) * 2005-01-14 2008-02-26 Halliburton Energy Services, Inc. Methods for fracturing subterranean wells
US20060169448A1 (en) * 2005-02-01 2006-08-03 Halliburton Energy Services, Inc. Self-degrading cement compositions and methods of using self-degrading cement compositions in subterranean formations
US7497258B2 (en) * 2005-02-01 2009-03-03 Halliburton Energy Services, Inc. Methods of isolating zones in subterranean formations using self-degrading cement compositions
US20060172894A1 (en) * 2005-02-02 2006-08-03 Halliburton Energy Services, Inc. Degradable particulate generation and associated methods
US20070298977A1 (en) * 2005-02-02 2007-12-27 Halliburton Energy Services, Inc. Degradable particulate generation and associated methods
US20060172895A1 (en) * 2005-02-02 2006-08-03 Halliburton Energy Services, Inc. Degradable particulate generation and associated methods
US7334636B2 (en) * 2005-02-08 2008-02-26 Halliburton Energy Services, Inc. Methods of creating high-porosity propped fractures using reticulated foam
US7318473B2 (en) * 2005-03-07 2008-01-15 Halliburton Energy Services, Inc. Methods relating to maintaining the structural integrity of deviated well bores
US7448451B2 (en) * 2005-03-29 2008-11-11 Halliburton Energy Services, Inc. Methods for controlling migration of particulates in a subterranean formation
US20060240995A1 (en) * 2005-04-23 2006-10-26 Halliburton Energy Services, Inc. Methods of using resins in subterranean formations
JP4605084B2 (en) * 2005-04-26 2011-01-05 東レ株式会社 Polylactic acid molded products
US8778375B2 (en) * 2005-04-29 2014-07-15 Advanced Cardiovascular Systems, Inc. Amorphous poly(D,L-lactide) coating
JP5289674B2 (en) * 2005-12-12 2013-09-11 三菱樹脂株式会社 Heat-shrinkable film, heat-shrink label using the film, molded product, and container
US7608567B2 (en) 2005-05-12 2009-10-27 Halliburton Energy Services, Inc. Degradable surfactants and methods for use
US9032641B2 (en) 2005-05-26 2015-05-19 Gala Industries, Inc. Method and apparatus for making crystalline polymeric pellets and granules
KR101379345B1 (en) * 2005-05-26 2014-03-28 갈라 인더스트리스 인코포레이티드 Method and Apparatus for Making Crystalline Polymeric Pellets and Granules
US7780903B2 (en) * 2005-06-01 2010-08-24 Kimberly-Clark Worldwide, Inc. Method of making fibers and nonwovens with improved properties
US20060276092A1 (en) * 2005-06-01 2006-12-07 Topolkaraev Vasily A Fibers and nonwovens with improved properties
US20060274474A1 (en) * 2005-06-01 2006-12-07 Lee Chung J Substrate Holder
US20060275547A1 (en) * 2005-06-01 2006-12-07 Lee Chung J Vapor Phase Deposition System and Method
US20060276345A1 (en) * 2005-06-07 2006-12-07 Halliburton Energy Servicers, Inc. Methods controlling the degradation rate of hydrolytically degradable materials
US20070014955A1 (en) * 2005-07-14 2007-01-18 Green Bay Packaging Inc. Printable polylactide film material, methods and labels made therefrom
DE102005033101A1 (en) * 2005-07-15 2007-01-25 Boehringer Ingelheim Pharma Gmbh & Co. Kg Resorbable polyether esters and their use for the manufacture of medical implants
US8394446B2 (en) * 2005-07-25 2013-03-12 Abbott Cardiovascular Systems Inc. Methods of providing antioxidants to implantable medical devices
US7785647B2 (en) * 2005-07-25 2010-08-31 Advanced Cardiovascular Systems, Inc. Methods of providing antioxidants to a drug containing product
US7484564B2 (en) * 2005-08-16 2009-02-03 Halliburton Energy Services, Inc. Delayed tackifying compositions and associated methods involving controlling particulate migration
US7595280B2 (en) 2005-08-16 2009-09-29 Halliburton Energy Services, Inc. Delayed tackifying compositions and associated methods involving controlling particulate migration
US20070049888A1 (en) * 2005-08-31 2007-03-01 Soerens Dave A Absorbent core comprising a multi-microlayer film
US20070049501A1 (en) * 2005-09-01 2007-03-01 Halliburton Energy Services, Inc. Fluid-loss control pills comprising breakers that comprise orthoesters and/or poly(orthoesters) and methods of use
US20070071963A1 (en) * 2005-09-27 2007-03-29 L&L Products, Inc. Design system
CN101296964A (en) * 2005-09-28 2008-10-29 塔特和莱利有限公司 Novel method for preparing polylactic acid
US20100000902A1 (en) * 2005-10-21 2010-01-07 Clemson University Composite polymeric materials from renewable resources
US7461697B2 (en) 2005-11-21 2008-12-09 Halliburton Energy Services, Inc. Methods of modifying particulate surfaces to affect acidic sites thereon
US20070114032A1 (en) * 2005-11-22 2007-05-24 Stegent Neil A Methods of consolidating unconsolidated particulates in subterranean formations
KR101277336B1 (en) * 2005-11-30 2013-06-20 도레이 카부시키가이샤 Polylactic acid resin multilayer sheet and molded body made of same
CN101400363B (en) 2006-01-18 2012-08-29 昌达生物科技公司 Pharmaceutical compositions with enhanced stability
US20070173416A1 (en) * 2006-01-20 2007-07-26 Halliburton Energy Services, Inc. Well treatment compositions for use in acidizing a well
US20080006405A1 (en) * 2006-07-06 2008-01-10 Halliburton Energy Services, Inc. Methods and compositions for enhancing proppant pack conductivity and strength
US7407010B2 (en) * 2006-03-16 2008-08-05 Halliburton Energy Services, Inc. Methods of coating particulates
US20070238384A1 (en) * 2006-03-20 2007-10-11 Ming Tang Articles, operating room drapes and methods of making and using the same
ES2337307T5 (en) 2006-04-14 2016-03-03 Biotec Biologische Naturverpackungen Gmbh & Co. Kg Multilayer sheet and manufacturing process
DE102006024568A1 (en) * 2006-05-23 2007-12-06 Huhtamaki Forchheim Zweigniederlassung Der Huhtamaki Deutschland Gmbh & Co. Kg Process for producing a biodegradable plastic film and film
US20070292691A1 (en) * 2006-06-19 2007-12-20 C.J. Multi-Tech Enterprises, Inc. Compostable reinforced paper, method of making same
EP2041346B1 (en) * 2006-07-14 2011-12-21 Kimberly-Clark Worldwide, Inc. Biodegradable polyactic acid for use in nonwoven webs
US8710172B2 (en) * 2006-07-14 2014-04-29 Kimberly-Clark Worldwide, Inc. Biodegradable aliphatic-aromatic copolyester for use in nonwoven webs
WO2008008067A1 (en) 2006-07-14 2008-01-17 Kimberly-Clark Worldwide, Inc. Biodegradable aliphatic polyester for use in nonwoven webs
US20080026959A1 (en) * 2006-07-25 2008-01-31 Halliburton Energy Services, Inc. Degradable particulates and associated methods
US20080026960A1 (en) * 2006-07-25 2008-01-31 Halliburton Energy Services, Inc. Degradable particulates and associated methods
US20080026955A1 (en) * 2006-07-25 2008-01-31 Halliburton Energy Services, Inc. Degradable particulates and associated methods
US7455112B2 (en) 2006-09-29 2008-11-25 Halliburton Energy Services, Inc. Methods and compositions relating to the control of the rates of acid-generating compounds in acidizing operations
EP2079767B1 (en) * 2006-10-11 2014-08-27 Tolmar Therapeutics, Inc. Preparation of biodegradable polyesters with low-burst properties by supercritical fluid extraction
US8076448B2 (en) * 2006-10-11 2011-12-13 Tolmar Therapeutics, Inc. Preparation of biodegradable polyesters with low-burst properties by supercritical fluid extraction
US7385020B2 (en) 2006-10-13 2008-06-10 3M Innovative Properties Company 2-octyl (meth)acrylate adhesive composition
US20080200890A1 (en) * 2006-12-11 2008-08-21 3M Innovative Properties Company Antimicrobial disposable absorbent articles
US9555167B2 (en) 2006-12-11 2017-01-31 3M Innovative Properties Company Biocompatible antimicrobial compositions
BRPI0622175A2 (en) * 2006-12-15 2011-12-27 Kimberly Clark Co Biodegradable polylactic acids for use in fiber formation
WO2008073099A1 (en) * 2006-12-15 2008-06-19 Kimberly-Clark Worldwide, Inc. Biodegradable polyesters for use in forming fibers
US8552111B2 (en) * 2007-01-12 2013-10-08 Kittrich Corporation Environmentally friendly polymeric textile coating
US20080188154A1 (en) * 2007-02-06 2008-08-07 Jen-Coat, Inc. Film laminate
KR101471220B1 (en) * 2007-03-16 2014-12-09 도레이 카부시키가이샤 Aliphatic polyester sheet and molded body composed of the same
EP2152807B1 (en) * 2007-05-16 2012-12-05 NatureWorks LLC Method for stabilizing polymers containing repeating lactic acid units, and stabilized polymers so made
US8147769B1 (en) 2007-05-16 2012-04-03 Abbott Cardiovascular Systems Inc. Stent and delivery system with reduced chemical degradation
ATE506472T1 (en) * 2007-08-22 2011-05-15 Kimberly Clark Co MULTI-COMPONENT BIODEGRADABLE FILAMENTS AND NON-WOVEN MATERIALS MADE THEREFROM
US20090062157A1 (en) * 2007-08-30 2009-03-05 Halliburton Energy Services, Inc. Methods and compositions related to the degradation of degradable polymers involving dehydrated salts and other associated methods
US20090112259A1 (en) * 2007-10-31 2009-04-30 Angiotech Pharmaceuticals, Inc. Recombinant expressed bioadsorbable polyhydroxyalkonate monofilament and multi-filaments self-retaining sutures
AT506038B1 (en) 2007-11-14 2015-02-15 Jungbunzlauer Austria Ag METHOD FOR THE PRODUCTION OF CYCLIC DIESTERS OF L, D AND D, L-MILKYLIC ACID
WO2009076541A1 (en) * 2007-12-11 2009-06-18 Toray Plastics (America), Inc. Process to produce biaxially oriented polylactic acid film at high transverse orientation rates
BRPI0722204A2 (en) * 2007-12-13 2014-11-04 Kimberly Clark Co "Biodegradable fibers formed from a thermoplastic composition containing polylactic acid and a polyester copolymer"
BRPI0821619B1 (en) * 2007-12-31 2018-12-18 Samyang Biopharmaceuticals Method for Preparation of an Amphiphilic Block Copolymer
US20090197780A1 (en) * 2008-02-01 2009-08-06 Weaver Jimmie D Ultrafine Grinding of Soft Materials
ES2706295T3 (en) 2008-02-21 2019-03-28 Ethicon Llc Method and apparatus for raising retainers in self-retaining sutures
US8377116B2 (en) * 2008-03-20 2013-02-19 Abbott Cardiovascular Systems Inc. Implantable medical device coatings with improved mechanical stability
US20090247710A1 (en) * 2008-03-31 2009-10-01 Purac Biochem B.V. Method for manufacturing stable polylactide
US20100151241A1 (en) * 2008-04-14 2010-06-17 3M Innovative Properties Company 2-Octyl (Meth)acrylate Adhesive Composition
US20090263458A1 (en) * 2008-04-21 2009-10-22 Lasse Daniel Efskind Material for surgical use in traumatology
KR101526636B1 (en) * 2008-05-30 2015-06-05 킴벌리-클라크 월드와이드, 인크. Polylactic acid fibers
MX345585B (en) * 2008-06-12 2017-02-07 3M Innovative Properties Co Melt blown fine fibers and methods of manufacture.
BRPI0910011A2 (en) 2008-06-12 2016-01-19 3M Innovative Properties Co durable hydrophilic composition, article and processes for manufacturing a durable hydrophilic composition
US20090319031A1 (en) * 2008-06-19 2009-12-24 Yunbing Wang Bioabsorbable Polymeric Stent With Improved Structural And Molecular Weight Integrity
FR2932797B1 (en) * 2008-06-20 2011-07-01 Colas Sa USE OF A BIOPOLYMER BINDER IN ROAD, PARAROUTIER OR CIVIL ENGINEERED APPLICATIONS.
EP2323788B1 (en) * 2008-08-15 2014-07-30 Toray Plastics (America) , Inc. Biaxially oriented polylactic acid film with high barrier
JP5077170B2 (en) * 2008-09-22 2012-11-21 株式会社日立プラントテクノロジー Process for producing polyhydroxycarboxylic acid
BRPI0921412A2 (en) * 2008-11-07 2016-01-05 Colgate Palmolive Co composition, packaging material, method of making a consumer packaging product, and consumer product
WO2010056822A2 (en) * 2008-11-13 2010-05-20 Conwed Plastics Llc Oxo-biodegradable netting
KR20110099777A (en) 2008-12-29 2011-09-08 쓰리엠 이노베이티브 프로퍼티즈 컴파니 Films having structured surface and methods for making the same
US20100167074A1 (en) * 2008-12-30 2010-07-01 Bunnelle William L Adhesive for difficult to adhere polymer coated board stock
BE1019313A3 (en) * 2009-01-12 2012-06-05 Futerro Sa CATALYTIC SYSTEMS FOR POLYMERIZATION OF CYCLIC ESTERS.
WO2010085608A1 (en) * 2009-01-23 2010-07-29 Surmodics Pharmaceuticals, Inc. Polymer mixtures comprising polymers having different non-repeating units and methods for making and using same
WO2010090496A2 (en) 2009-02-09 2010-08-12 주식회사 엘지화학 Polylactide resin and preparation method thereof
TW201031524A (en) * 2009-02-16 2010-09-01 Wei Mon Ind Co Ltd Paperboard with polylactic acid
US20100212906A1 (en) * 2009-02-20 2010-08-26 Halliburton Energy Services, Inc. Method for diversion of hydraulic fracture treatments
CN102439210B (en) 2009-03-31 2015-12-16 3M创新有限公司 Non woven fibre web of dimensionally stable and production and preparation method thereof
JP5340818B2 (en) * 2009-06-15 2013-11-13 ユニチカ株式会社 Acid end-capped polylactic acid and method for producing the same
US9150004B2 (en) * 2009-06-19 2015-10-06 Toray Plastics (America), Inc. Biaxially oriented polylactic acid film with improved heat seal properties
WO2010151872A1 (en) * 2009-06-26 2010-12-29 Toray Plastics (America) , Inc. Biaxially oriented polylactic acid film with improved moisture barrier
JP5577764B2 (en) * 2009-07-06 2014-08-27 株式会社リコー Copolymer resin composition, molded article, and method for producing copolymer resin composition
US9889238B2 (en) * 2009-07-21 2018-02-13 Abbott Cardiovascular Systems Inc. Biodegradable stent with adjustable degradation rate
US8889823B2 (en) * 2009-07-21 2014-11-18 Abbott Cardiovascular Systems Inc. Method to make poly(L-lactide) stent with tunable degradation rate
US20110052847A1 (en) * 2009-08-27 2011-03-03 Roberts Danny H Articles of manufacture from renewable resources
EP2480710B1 (en) * 2009-09-25 2018-01-24 Toray Plastics (America) , Inc. Multi-layer high moisture barrier polylactic acid film and its method of forming
US9221213B2 (en) 2009-09-25 2015-12-29 Toray Plastics (America), Inc. Multi-layer high moisture barrier polylactic acid film
EP2499190B1 (en) 2009-11-10 2013-11-06 3M Innovative Properties Company Method for making polylactide films
TWI445606B (en) * 2009-12-02 2014-07-21 Chi Mei Corp Preparation of bead-like particles of lactic acid polymers
BE1019059A3 (en) 2009-12-03 2012-02-07 Futerro Sa METHOD FOR MASS POLYMERIZATION OF LACTIDE
AU2010330866A1 (en) * 2009-12-17 2012-07-12 3M Innovative Properties Company Dimensionally stable nonwoven fibrous webs, melt blown fine fibers, and methods of making and using the same
WO2011084670A1 (en) 2009-12-17 2011-07-14 3M Innovative Properties Company Dimensionally stable nonwoven fibrous webs and methods of making and using the same
RU2478107C2 (en) * 2009-12-25 2013-03-27 Государственное образовательное учреждение высшего профессионального образования Российский химико-технологический университет им. Д.И. Менделеева (РХТУ им. Д.И. Менделеева) Method of producing biodegradable polymer
AU2011218854B2 (en) 2010-02-23 2015-03-12 3M Innovative Properties Company Dimensionally stable nonwoven fibrous webs and methods of making and using the same
US20110319509A1 (en) * 2010-03-23 2011-12-29 Polynew, Inc. Polymer composites incorporating stereocomplexation
US8604101B2 (en) * 2010-03-24 2013-12-10 Basf Se Process for producing aqueous dispersions of thermoplastic polyesters
BR112012023413A2 (en) 2010-03-24 2018-05-08 Basf Se process for producing aqueous dispersions of thermoplastic polymers, aqueous polymer dispersion, use of an aqueous polymer dispersion, and thermoplastic polyester.
CN102361935B (en) * 2010-03-30 2015-10-14 日东电工株式会社 Polylactic acid film or thin slice and manufacture method thereof
US9492962B2 (en) 2010-03-31 2016-11-15 Toray Plastics (America), Inc. Biaxially oriented polylactic acid film with reduced noise level and improved moisture barrier
EP2552689B1 (en) 2010-03-31 2017-10-25 Toray Plastics (America) , Inc. Biaxially oriented polyactic acid film with reduced noise level
DE202011110978U1 (en) 2010-06-21 2017-11-27 Lg Chem, Ltd. Polylactide resin with excellent heat resistance
TW201221714A (en) 2010-10-14 2012-06-01 3M Innovative Properties Co Dimensionally stable nonwoven fibrous webs and methods of making and using the same
US8461262B2 (en) 2010-12-07 2013-06-11 Kimberly-Clark Worldwide, Inc. Polylactic acid fibers
WO2012144511A1 (en) * 2011-04-22 2012-10-26 株式会社クレハ Biodegradable aliphatic polyester particles, and process for producing same
US8709070B2 (en) 2011-05-10 2014-04-29 Abbott Cardiovascular Systems Inc. Bioabsorbable scaffold with particles providing delayed acceleration of degradation
EP2758594A1 (en) 2011-09-23 2014-07-30 Basf Se Use of an aqueous dispersion of biodegradable polyesters
FR2991230B1 (en) * 2012-05-31 2015-02-20 Ahlstroem Oy MULTILAYER COMPLEX COMPRISING A LAYER BASED ON A BIODEGRADABLE POLYMER AND A SUPPORT BASED ON CELLULOSIC FIBERS; METHOD OF MANUFACTURE AND USE
MX356109B (en) 2012-10-12 2018-05-15 3M Innovative Properties Co Multi-layer articles.
EP2727950A1 (en) * 2012-11-02 2014-05-07 Rhein Chemie Rheinau GmbH Method for drying of plastics on the basis of polyester resins
FR3002537B1 (en) * 2013-02-26 2015-04-24 Ipsen Pharma NEW PROCESS FOR PURIFYING POLYESTERS
WO2014155213A2 (en) 2013-03-26 2014-10-02 Indian Institute Of Technology Madras Catalysts for poly(lactide) synthesis and uses thereof
US9901663B2 (en) 2013-05-06 2018-02-27 Abbott Cardiovascular Systems Inc. Hollow stent filled with a therapeutic agent formulation
EP3052567A1 (en) 2013-09-30 2016-08-10 3M Innovative Properties Company Compositions, wipes, and methods
JP2016536474A (en) 2013-09-30 2016-11-24 スリーエム イノベイティブ プロパティズ カンパニー Fiber and wipe with epoxidized fatty acid ester disposed thereon and method
JP2016535174A (en) 2013-09-30 2016-11-10 スリーエム イノベイティブ プロパティズ カンパニー Fibers, wipes, and methods
KR102189677B1 (en) 2014-02-10 2020-12-11 삼성전자주식회사 Preparation method of polylactic acid, polylactic acid resin prepared therefrom, resin composition comprising the resin, and catalyst system for preparing polylactic acid
JP2015205994A (en) * 2014-04-21 2015-11-19 東洋紡株式会社 Polylactic acid base resin for thermofusion type road-marking coating material and thermofusion type road-marking coating composition
US9512338B2 (en) 2014-04-29 2016-12-06 Greif Packaging Llc Method for manufacturing an adhesive compound for use in the production of corrugated paperboard
US9675478B2 (en) 2014-06-11 2017-06-13 Abbott Cardiovascular Systems Inc. Solvent method for forming a polymer scaffolding
US9381280B2 (en) 2014-06-13 2016-07-05 Abbott Cardiovascular Systems Inc. Plasticizers for a biodegradable scaffolding and methods of forming same
CA2967936C (en) 2014-11-14 2023-10-31 Schlumberger Canada Limited Well treatments for diversion or zonal isolation
US10716264B2 (en) 2014-12-19 2020-07-21 Selfeco LLC Biodegradable horticulture container
US10470378B2 (en) 2014-12-19 2019-11-12 Selfeco LLC Biodegradable horticulture container
US10143318B2 (en) 2015-01-19 2018-12-04 Selfeco LLC Food display and service articles
USD775999S1 (en) 2015-03-16 2017-01-10 Selfeco LLC Plant pot
US9872442B2 (en) 2015-03-16 2018-01-23 Selfeco LLC Biodegradable shield for plant protection
RU2624905C2 (en) * 2015-12-21 2017-07-10 Федеральное государственное бюджетное учреждение "Национальный исследовательский центр "Курчатовский институт" Method for preparing catalyst for biodiversive aliphatic synthesis of complex polyesters
KR20170093028A (en) * 2016-02-04 2017-08-14 에스케이케미칼주식회사 Flexible polylactic acid resin composition comprising a water scavenger
FR3060582A1 (en) 2016-12-21 2018-06-22 Compagnie Generale Des Etablissements Michelin PROCESS FOR THE PREPARATION OF POLYDIENE / POLYLACTIDE COPOLYMERS BY REACTIVE EXTRUSION
FR3060454A1 (en) 2016-12-21 2018-06-22 Compagnie Generale Des Etablissements Michelin RUBBER COMPOSITION COMPRISING A POLYDIENE / POLYLACTIDE COPOLYMER
EP3461857A1 (en) * 2017-09-28 2019-04-03 Helmholtz-Zentrum Geesthacht Zentrum für Material- und Küstenforschung GmbH Surface-functionalised polymeric object and method of its production
US11220126B2 (en) 2017-12-15 2022-01-11 3M Innovative Properties Company Textured printable nonwoven media
FR3082519B1 (en) 2018-06-19 2020-11-20 Michelin & Cie ELASTOMERIC BLEND INCLUDING PLLA AND PDLA
DE102019200596A1 (en) 2019-01-17 2020-07-23 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. USE OF ADDITIVE COMPOSITION FOR CONTROLLED ACCELERATED DISASSEMBLY OF CONDENSATION POLYMERS
JP2022525475A (en) * 2019-03-18 2022-05-16 ノボマー, インコーポレイテッド Membrane separation system and its applications
US20220306799A1 (en) * 2019-06-03 2022-09-29 Total Corbion Pla Bv Process for Preparing Stabilized Aliphatic Polyester, and Compositions Obtained Therewith
MX2021015331A (en) * 2019-06-13 2022-01-18 Natureworks Llc Fast-hydrolyzing polylactide resin compositions.
AU2022252189A1 (en) 2021-03-31 2023-10-12 Natureworks Llc Melt-stable polylactide resin compositions containing phosphite esters
CN115491006A (en) * 2022-10-10 2022-12-20 金发科技股份有限公司 Polylactic acid composition and preparation method and application thereof

Citations (92)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE267826C (en) * 1912-12-28 1913-12-02 Chemische Werke Process for the preparation of lactide
US1095205A (en) * 1913-05-15 1914-05-05 Chemische Werke Vorm Dr Heinrich Byk Manufacture of lactid.
US1849107A (en) * 1928-05-12 1932-03-15 Celanese Corp Synthetic resin and method of making the same
US1995970A (en) * 1931-04-04 1935-03-26 Du Pont Polymeric lactide resin
US2396994A (en) * 1944-01-18 1946-03-19 Nasa Condensation products of hydroxy carboxylic acids
US2703316A (en) * 1951-06-05 1955-03-01 Du Pont Polymers of high melting lactide
US2758987A (en) * 1952-06-05 1956-08-14 Du Pont Optically active homopolymers containing but one antipodal species of an alpha-monohydroxy monocarboxylic acid
DE1083275B (en) * 1959-07-02 1960-06-15 Dynamit Nobel Ag Process for the production of lactide
US2951828A (en) * 1957-03-04 1960-09-06 Boehringer Sohn Ingelheim Process for the production of bead polymerizates from cyclic internal esters of alpha-hydroxy carboxylic acids
US3268487A (en) * 1963-12-23 1966-08-23 Shell Oil Co Process for polymerization of lactides
GB1040168A (en) * 1963-11-08 1966-08-24 Du Pont High molecular weight polylactides and a process for their preparation
US3322791A (en) * 1963-09-26 1967-05-30 Ethicon Inc Preparation of optically active lactides
GB1108720A (en) * 1966-10-10 1968-04-03 Wolfen Filmfab Veb Process for the manufacture of cyclic ester anhydrides of ª‡-hydroxy-carboxylic acids
CA808731A (en) * 1969-03-18 A. Fouty Roger Preparation of high molecular weight polylactides
DE1543958A1 (en) * 1966-01-20 1970-02-05 Wolfen Filmfab Veb Process for the preparation of cyclic ester anhydrides of alpha-hydroxycarboxylic acids
US3531561A (en) * 1965-04-20 1970-09-29 Ethicon Inc Suture preparation
CA863673A (en) * 1971-02-16 K. Schneider Allan Absorbable suture
US3636956A (en) * 1970-05-13 1972-01-25 Ethicon Inc Polylactide sutures
CA923245A (en) * 1970-04-14 1973-03-20 Ethicon Preparation of high molecular weight polylactides
US3772420A (en) * 1968-12-23 1973-11-13 American Cyanamid Co Method for improving the in-vivo strength of polyglycolic acid
US3773919A (en) * 1969-10-23 1973-11-20 Du Pont Polylactide-drug mixtures
GB1351409A (en) * 1971-02-23 1974-05-01 Du Pont Sustained release pharmaceutical compositions for topical appli cation
US3839297A (en) * 1971-11-22 1974-10-01 Ethicon Inc Use of stannous octoate catalyst in the manufacture of l(-)lactide-glycolide copolymer sutures
US3887699A (en) * 1969-03-24 1975-06-03 Seymour Yolles Biodegradable polymeric article for dispensing drugs
US3912692A (en) * 1973-05-03 1975-10-14 American Cyanamid Co Process for polymerizing a substantially pure glycolide composition
US4045418A (en) * 1975-01-28 1977-08-30 Gulf Oil Corporation Copolymers of D,L-lactide and epsilon caprolactone
US4249531A (en) * 1979-07-05 1981-02-10 Alza Corporation Bioerodible system for delivering drug manufactured from poly(carboxylic acid)
US4273920A (en) * 1979-09-12 1981-06-16 Eli Lilly And Company Polymerization process and product
US4279249A (en) * 1978-10-20 1981-07-21 Agence Nationale De Valorisation De La Recherche (Anvar) New prosthesis parts, their preparation and their application
EP0052510A2 (en) * 1980-11-18 1982-05-26 Syntex (U.S.A.) Inc. Microencapsulation of water soluble polypeptides
EP0107591A2 (en) * 1982-10-22 1984-05-02 United States Surgical Corporation Absorbable surgical devices
GB2145422A (en) * 1983-08-26 1985-03-27 Sandoz Ltd Novel poly-esters, their preparation and pharmacological use thereof
US4595713A (en) * 1985-01-22 1986-06-17 Hexcel Corporation Medical putty for tissue augmentation
US4643734A (en) * 1983-05-05 1987-02-17 Hexcel Corporation Lactide/caprolactone polymer, method of making the same, composites thereof, and prostheses produced therefrom
US4677191A (en) * 1984-07-06 1987-06-30 Wada Pure Chemical Ind., Ltd. Copolymer and method for producing the same
US4719246A (en) * 1986-12-22 1988-01-12 E. I. Du Pont De Nemours And Company Polylactide compositions
US4727163A (en) * 1985-07-11 1988-02-23 E. I. Du Pont De Nemours And Company Process for preparing highly pure cyclic esters
US4728721A (en) * 1985-05-07 1988-03-01 Takeda Chemical Industries, Ltd. Polymer, production and use thereof
DE3632103A1 (en) * 1986-09-20 1988-03-24 Boehringer Ingelheim Kg Process for the preparation of lactide
US4766182A (en) * 1986-12-22 1988-08-23 E. I. Du Pont De Nemours And Company Polylactide compositions
US4789726A (en) * 1986-04-18 1988-12-06 Imperial Chemical Industries Plc Manufacture of polyesters
US4797468A (en) * 1986-12-19 1989-01-10 Akzo N.V. Preparation of polylactic acid and copolymers of lactic acids
EP0299730A2 (en) * 1987-07-14 1989-01-18 MITSUI TOATSU CHEMICALS, Inc. Process of preparing dl-lactic acid-glycolic acid-copolymer
US4800219A (en) * 1986-12-22 1989-01-24 E. I. Du Pont De Nemours And Company Polylactide compositions
EP0314245A1 (en) * 1987-10-28 1989-05-03 Purac Biochem B.V. Method for the preparation of a polymer lactide
US4835293A (en) * 1987-02-24 1989-05-30 E. I. Du Pont De Nemours And Company Atmospheric pressure process for preparing pure cyclic esters
US4902515A (en) * 1988-04-28 1990-02-20 E. I. Dupont De Nemours And Company Polylactide compositions
WO1990001521A1 (en) * 1988-08-08 1990-02-22 Battelle Memorial Institute Degradable thermoplastic from lactides
US4950258A (en) * 1988-01-28 1990-08-21 Japan Medical Supply Co., Ltd. Plastic molded articles with shape memory property
US4960866A (en) * 1986-12-06 1990-10-02 Boehringer Ingelheim Zentrale Catalyst-free resorbable homopolymers and copolymers
US4981696A (en) * 1986-12-22 1991-01-01 E. I. Du Pont De Nemours And Company Polylactide compositions
US4983745A (en) * 1987-06-16 1991-01-08 Boehringer Ingelheim Kg Meso-lactide, processes for preparing it and polymers and copolymers produced therefrom
US4990222A (en) * 1986-10-24 1991-02-05 Boehringer Ingelheim Kg Process for the purification of thermolabile compounds by distillation
WO1991002015A1 (en) * 1989-08-08 1991-02-21 The Pennsylvania Research Corporation Hydrodegradable polyesters
US5011946A (en) * 1989-05-26 1991-04-30 Boehringer Ingelheim Gmbh Process for preparing D,L-Lactide
WO1991006601A1 (en) * 1989-11-02 1991-05-16 Allied-Signal Inc. Biodegradable polymeric materials and articles fabricated therefrom
US5023350A (en) * 1990-05-24 1991-06-11 E. I. Du Pont De Nemours And Company Process for the purification of cyclic esters
US5023349A (en) * 1990-05-08 1991-06-11 E. I. Du Pont De Nemours And Company Continuous process for rapid conversion of oligomers to cyclic esters
US5041529A (en) * 1988-11-07 1991-08-20 Mitsui Toatsu Chemicals, Inc. Preparation process for bioabsorbable polyester
US5043458A (en) * 1990-05-03 1991-08-27 E. I. Du Pont De Nemours And Company One-step continuous process for preparing cyclic esters
US5053522A (en) * 1987-03-19 1991-10-01 Boehringer Ingelheim Kg Process for the preparation of lactide
WO1991017155A1 (en) * 1990-05-03 1991-11-14 E.I. Du Pont De Nemours And Company Improved process for the rapid production of cyclic esters
US5076983A (en) * 1990-07-16 1991-12-31 E. I. Du Pont De Nemours And Company Polyhydroxy acid films
WO1992000292A1 (en) * 1990-06-28 1992-01-09 E.I. Du Pont De Nemours And Company Continuous catalyzed vapor phase dimeric cyclic ester process
WO1992000974A1 (en) * 1990-07-13 1992-01-23 E.I. Du Pont De Nemours And Company High yield recycle process for lactide
US5097005A (en) * 1990-05-11 1992-03-17 E. I. Du Pont De Nemours And Company Novel copolyesters and their use in compostable products such as disposable diapers
WO1992004413A1 (en) * 1990-09-06 1992-03-19 Biopak Technology Ltd Packaging thermoplastics from lactic acid
WO1992004410A1 (en) * 1990-09-11 1992-03-19 E.I. Du Pont De Nemours And Company Films containing polyhydroxy acids and a compatibilizer
WO1992004412A1 (en) * 1990-09-11 1992-03-19 E.I. Du Pont De Nemours And Company Films containing polyhydroxy acids
WO1992005168A1 (en) * 1990-09-18 1992-04-02 Biopak Technology Ltd. Catalytic production of lactide directly from lactic acid
WO1992005167A1 (en) * 1990-09-18 1992-04-02 Biopak Technology Ltd Lactide production from dehydration of aqueous lactic acid feed
WO1992005311A1 (en) * 1990-09-26 1992-04-02 E.I. Du Pont De Nemours And Company Cellulosic pulp bonded by polyhydroxy acid resins
EP0481732A1 (en) * 1990-10-16 1992-04-22 Takeda Chemical Industries, Ltd. Prolonged release preparation and polymers thereof
US5108399A (en) * 1988-09-17 1992-04-28 Boehringer Ingelheim Gmbh Device for osteosynthesis and process for producing it
US5132397A (en) * 1991-04-02 1992-07-21 Polysar Financial Services S.A. 4-valerolactone copolymers
US5134171A (en) * 1990-07-16 1992-07-28 E. I. Du Pont De Nemours And Company Degradable foam materials
US5136017A (en) * 1991-02-22 1992-08-04 Polysar Financial Services S.A. Continuous lactide polymerization
US5142023A (en) * 1992-01-24 1992-08-25 Cargill, Incorporated Continuous process for manufacture of lactide polymers with controlled optical purity
WO1992015340A1 (en) * 1991-03-04 1992-09-17 Guidor Ab Bioresorbable material and an article of manufacture made of such material for medical use
US5149833A (en) * 1989-05-26 1992-09-22 Boehringer Ingelheim Gmbh Process for preparing D,L-Lactide
EP0507554A1 (en) * 1991-04-01 1992-10-07 MITSUI TOATSU CHEMICALS, Inc. Degradable foam, process for its preparation and use of same
JPH04283227A (en) * 1991-03-11 1992-10-08 Mitsui Toatsu Chem Inc Hydrolyzable resin composition
EP0510998A2 (en) * 1991-04-26 1992-10-28 MITSUI TOATSU CHEMICALS, Inc. Porous film
EP0515203A2 (en) * 1991-05-24 1992-11-25 Camelot Technologies Inc. Polylactide blends
US5180765A (en) * 1988-08-08 1993-01-19 Biopak Technology, Ltd. Biodegradable packaging thermoplastics from lactides
WO1993002075A1 (en) * 1991-07-24 1993-02-04 E.I. Du Pont De Nemours And Company Thin film depolymerization to dimeric cyclic esters
EP0532154A2 (en) * 1991-09-12 1993-03-17 Novacor Chemicals (International) S.A. Process for devolatilization of polylactides
EP0533314A2 (en) * 1991-09-17 1993-03-24 Novacor Chemicals (International) S.A. Biodegradable polyester compositions
US5223546A (en) * 1991-04-24 1993-06-29 Mitsui Toatsu Chemicals, Inc. High polymer network
US5225490A (en) * 1989-11-08 1993-07-06 Director-General Of Agency Of Industrial Science And Technology Biodisintegrable thermoplastic resin moldings and a process for producing same
US5296229A (en) * 1991-07-19 1994-03-22 Solvay (Societe Anonyme) Flexible, elastic and biodegradable film made of polymer based on lactic acid, capable of being suitable especially for the production of medical dressings
US5338822A (en) * 1992-10-02 1994-08-16 Cargill, Incorporated Melt-stable lactide polymer composition and process for manufacture thereof

Family Cites Families (36)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA683673A (en) * 1953-09-26 1964-04-07 W. Davis John Disc brake for vehicles
GB808731A (en) * 1956-01-20 1959-02-11 Du Pont Preparation of platinum metal catalysts
US3332791A (en) * 1964-05-12 1967-07-25 Rayonier Inc Process for producing portland cement compositions
JPS433017Y1 (en) * 1964-12-28 1968-02-07
JPS438614Y1 (en) * 1965-01-21 1968-04-16
JPS432949Y1 (en) * 1965-08-26 1968-02-07
NL6607189A (en) * 1966-05-25 1967-11-27
US4343931A (en) * 1979-12-17 1982-08-10 Minnesota Mining And Manufacturing Company Synthetic absorbable surgical devices of poly(esteramides)
US4529792A (en) * 1979-12-17 1985-07-16 Minnesota Mining And Manufacturing Company Process for preparing synthetic absorbable poly(esteramides)
US4343939A (en) * 1981-04-22 1982-08-10 American Cyanamid Company Glycolic acid esters and amides of bis(p-disubstitutedaminophenyl)carbinol
DE3149358A1 (en) * 1981-12-12 1983-06-16 Basf Ag, 6700 Ludwigshafen THERMOPLASTIC MOLDING
US4441496A (en) * 1982-02-08 1984-04-10 Ethicon, Inc. Copolymers of p-dioxanone and 2,5-morpholinediones and surgical devices formed therefrom having accelerated absorption characteristics
HU194939B (en) * 1983-12-22 1988-03-28 Chinoin Gyogyszer Es Vegyeszet Process for producing alpha- beta- and gamma cyclodextrine of high yield capacity
US4611023A (en) * 1984-02-03 1986-09-09 Ciba-Geigy Corporation Di-(substituted hydroxyphenylthio) alkane and cycloalkane stabilizers and stabilized compositions
US5444113A (en) * 1988-08-08 1995-08-22 Ecopol, Llc End use applications of biodegradable polymers
US5216050A (en) * 1988-08-08 1993-06-01 Biopak Technology, Ltd. Blends of polyactic acid
US5502158A (en) * 1988-08-08 1996-03-26 Ecopol, Llc Degradable polymer composition
US5424346A (en) * 1988-08-08 1995-06-13 Ecopol, Llc Biodegradable replacement of crystal polystyrene
US5252642A (en) * 1989-03-01 1993-10-12 Biopak Technology, Ltd. Degradable impact modified polyactic acid
US5124023A (en) * 1988-11-28 1992-06-23 Union Oil Company Of California Continuous removal of polynuclear aromatics from hydrocarbon recycle oil
DE69017958T2 (en) * 1989-06-29 1995-12-14 Well Equip Ltd Borehole impact device.
WO1991013207A1 (en) * 1990-02-21 1991-09-05 Pulp And Paper Research Institute Of Canada POLY-β-HYDROXYALKANOATES FOR USE IN FIBRE CONSTRUCTS AND FILMS
US5302694A (en) * 1990-02-21 1994-04-12 Boehringer Ingelheim Gmbh Process for preparing polyesters based on hydroxycarboxylic acids
US5210296A (en) * 1990-11-19 1993-05-11 E. I. Du Pont De Nemours And Company Recovery of lactate esters and lactic acid from fermentation broth
JP3167411B2 (en) * 1991-04-26 2001-05-21 三井化学株式会社 Porous film
CA2068368A1 (en) * 1991-05-13 1992-11-14 Masanobu Ajioka Degradable laminate composition
DE69223145T2 (en) * 1991-07-03 1998-04-30 Sterling Diagnostic Imaging COMBINATION OF FILM AND ULTRAVIOLET-EMITTING SCREEN FOR IMPROVED RADIOLOGICAL EVALUATIONS
US5296282A (en) * 1991-08-12 1994-03-22 E. I. Du Pont De Nemours And Company Degradable repellant coated articles
US5233546A (en) * 1991-08-14 1993-08-03 Hewlett-Packard Company Anti-alias filtering apparatus for frequency domain measurements
US5351767A (en) * 1991-11-07 1994-10-04 Globral Marine Inc. Drill pipe handling
US5229528A (en) * 1991-11-22 1993-07-20 E. I. Du Pont De Nemours And Company Rapid depolymerization of polyhydroxy acids
US5236560A (en) * 1992-03-13 1993-08-17 E. I. Du Pont De Nemours And Company Solventless dimeric cyclic ester distillation process
DE69322155T2 (en) * 1992-10-02 1999-08-19 Cargill Inc PAPER WITH A COATING FROM MELT-STABLE POLYMER AND ITS METHOD FOR THE PRODUCTION THEREOF
US5252646A (en) * 1992-10-29 1993-10-12 National Starch And Chemical Investment Holding Corporation Polylactide containing hot melt adhesive
US5202413A (en) * 1993-02-16 1993-04-13 E. I. Du Pont De Nemours And Company Alternating (ABA)N polylactide block copolymers
US5359026A (en) * 1993-07-30 1994-10-25 Cargill, Incorporated Poly(lactide) copolymer and process for manufacture thereof

Patent Citations (95)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA863673A (en) * 1971-02-16 K. Schneider Allan Absorbable suture
CA808731A (en) * 1969-03-18 A. Fouty Roger Preparation of high molecular weight polylactides
DE267826C (en) * 1912-12-28 1913-12-02 Chemische Werke Process for the preparation of lactide
US1095205A (en) * 1913-05-15 1914-05-05 Chemische Werke Vorm Dr Heinrich Byk Manufacture of lactid.
US1849107A (en) * 1928-05-12 1932-03-15 Celanese Corp Synthetic resin and method of making the same
US1995970A (en) * 1931-04-04 1935-03-26 Du Pont Polymeric lactide resin
US2396994A (en) * 1944-01-18 1946-03-19 Nasa Condensation products of hydroxy carboxylic acids
US2703316A (en) * 1951-06-05 1955-03-01 Du Pont Polymers of high melting lactide
US2758987A (en) * 1952-06-05 1956-08-14 Du Pont Optically active homopolymers containing but one antipodal species of an alpha-monohydroxy monocarboxylic acid
US2951828A (en) * 1957-03-04 1960-09-06 Boehringer Sohn Ingelheim Process for the production of bead polymerizates from cyclic internal esters of alpha-hydroxy carboxylic acids
DE1083275B (en) * 1959-07-02 1960-06-15 Dynamit Nobel Ag Process for the production of lactide
US3322791A (en) * 1963-09-26 1967-05-30 Ethicon Inc Preparation of optically active lactides
GB1040168A (en) * 1963-11-08 1966-08-24 Du Pont High molecular weight polylactides and a process for their preparation
US3268487A (en) * 1963-12-23 1966-08-23 Shell Oil Co Process for polymerization of lactides
US3531561A (en) * 1965-04-20 1970-09-29 Ethicon Inc Suture preparation
DE1543958A1 (en) * 1966-01-20 1970-02-05 Wolfen Filmfab Veb Process for the preparation of cyclic ester anhydrides of alpha-hydroxycarboxylic acids
GB1108720A (en) * 1966-10-10 1968-04-03 Wolfen Filmfab Veb Process for the manufacture of cyclic ester anhydrides of ª‡-hydroxy-carboxylic acids
US3772420A (en) * 1968-12-23 1973-11-13 American Cyanamid Co Method for improving the in-vivo strength of polyglycolic acid
US3887699A (en) * 1969-03-24 1975-06-03 Seymour Yolles Biodegradable polymeric article for dispensing drugs
US3773919A (en) * 1969-10-23 1973-11-20 Du Pont Polylactide-drug mixtures
CA923245A (en) * 1970-04-14 1973-03-20 Ethicon Preparation of high molecular weight polylactides
US3636956A (en) * 1970-05-13 1972-01-25 Ethicon Inc Polylactide sutures
GB1351409A (en) * 1971-02-23 1974-05-01 Du Pont Sustained release pharmaceutical compositions for topical appli cation
US3839297A (en) * 1971-11-22 1974-10-01 Ethicon Inc Use of stannous octoate catalyst in the manufacture of l(-)lactide-glycolide copolymer sutures
US3912692A (en) * 1973-05-03 1975-10-14 American Cyanamid Co Process for polymerizing a substantially pure glycolide composition
US4045418A (en) * 1975-01-28 1977-08-30 Gulf Oil Corporation Copolymers of D,L-lactide and epsilon caprolactone
US4279249A (en) * 1978-10-20 1981-07-21 Agence Nationale De Valorisation De La Recherche (Anvar) New prosthesis parts, their preparation and their application
US4249531A (en) * 1979-07-05 1981-02-10 Alza Corporation Bioerodible system for delivering drug manufactured from poly(carboxylic acid)
US4273920A (en) * 1979-09-12 1981-06-16 Eli Lilly And Company Polymerization process and product
EP0052510A2 (en) * 1980-11-18 1982-05-26 Syntex (U.S.A.) Inc. Microencapsulation of water soluble polypeptides
EP0107591A2 (en) * 1982-10-22 1984-05-02 United States Surgical Corporation Absorbable surgical devices
US4643734A (en) * 1983-05-05 1987-02-17 Hexcel Corporation Lactide/caprolactone polymer, method of making the same, composites thereof, and prostheses produced therefrom
GB2145422A (en) * 1983-08-26 1985-03-27 Sandoz Ltd Novel poly-esters, their preparation and pharmacological use thereof
US4677191A (en) * 1984-07-06 1987-06-30 Wada Pure Chemical Ind., Ltd. Copolymer and method for producing the same
US4683288A (en) * 1984-07-06 1987-07-28 Waco Pure Chemical Ind. Inc. Polymer and its production
US4595713A (en) * 1985-01-22 1986-06-17 Hexcel Corporation Medical putty for tissue augmentation
US4728721A (en) * 1985-05-07 1988-03-01 Takeda Chemical Industries, Ltd. Polymer, production and use thereof
US4727163A (en) * 1985-07-11 1988-02-23 E. I. Du Pont De Nemours And Company Process for preparing highly pure cyclic esters
US4789726A (en) * 1986-04-18 1988-12-06 Imperial Chemical Industries Plc Manufacture of polyesters
DE3632103A1 (en) * 1986-09-20 1988-03-24 Boehringer Ingelheim Kg Process for the preparation of lactide
US4990222A (en) * 1986-10-24 1991-02-05 Boehringer Ingelheim Kg Process for the purification of thermolabile compounds by distillation
US4960866A (en) * 1986-12-06 1990-10-02 Boehringer Ingelheim Zentrale Catalyst-free resorbable homopolymers and copolymers
US4797468A (en) * 1986-12-19 1989-01-10 Akzo N.V. Preparation of polylactic acid and copolymers of lactic acids
US4800219A (en) * 1986-12-22 1989-01-24 E. I. Du Pont De Nemours And Company Polylactide compositions
US4719246A (en) * 1986-12-22 1988-01-12 E. I. Du Pont De Nemours And Company Polylactide compositions
US4981696A (en) * 1986-12-22 1991-01-01 E. I. Du Pont De Nemours And Company Polylactide compositions
US4766182A (en) * 1986-12-22 1988-08-23 E. I. Du Pont De Nemours And Company Polylactide compositions
US4835293A (en) * 1987-02-24 1989-05-30 E. I. Du Pont De Nemours And Company Atmospheric pressure process for preparing pure cyclic esters
US5053522A (en) * 1987-03-19 1991-10-01 Boehringer Ingelheim Kg Process for the preparation of lactide
US4983745A (en) * 1987-06-16 1991-01-08 Boehringer Ingelheim Kg Meso-lactide, processes for preparing it and polymers and copolymers produced therefrom
EP0299730A2 (en) * 1987-07-14 1989-01-18 MITSUI TOATSU CHEMICALS, Inc. Process of preparing dl-lactic acid-glycolic acid-copolymer
EP0314245A1 (en) * 1987-10-28 1989-05-03 Purac Biochem B.V. Method for the preparation of a polymer lactide
US5053485A (en) * 1987-10-28 1991-10-01 C.C.A. Biochem B.V. Polymer lactide, method for preparing it and a composition containing it
US4950258A (en) * 1988-01-28 1990-08-21 Japan Medical Supply Co., Ltd. Plastic molded articles with shape memory property
US4902515A (en) * 1988-04-28 1990-02-20 E. I. Dupont De Nemours And Company Polylactide compositions
WO1990001521A1 (en) * 1988-08-08 1990-02-22 Battelle Memorial Institute Degradable thermoplastic from lactides
US5180765A (en) * 1988-08-08 1993-01-19 Biopak Technology, Ltd. Biodegradable packaging thermoplastics from lactides
US5108399A (en) * 1988-09-17 1992-04-28 Boehringer Ingelheim Gmbh Device for osteosynthesis and process for producing it
US5041529A (en) * 1988-11-07 1991-08-20 Mitsui Toatsu Chemicals, Inc. Preparation process for bioabsorbable polyester
US5011946A (en) * 1989-05-26 1991-04-30 Boehringer Ingelheim Gmbh Process for preparing D,L-Lactide
US5149833A (en) * 1989-05-26 1992-09-22 Boehringer Ingelheim Gmbh Process for preparing D,L-Lactide
WO1991002015A1 (en) * 1989-08-08 1991-02-21 The Pennsylvania Research Corporation Hydrodegradable polyesters
WO1991006601A1 (en) * 1989-11-02 1991-05-16 Allied-Signal Inc. Biodegradable polymeric materials and articles fabricated therefrom
US5225490A (en) * 1989-11-08 1993-07-06 Director-General Of Agency Of Industrial Science And Technology Biodisintegrable thermoplastic resin moldings and a process for producing same
WO1991017155A1 (en) * 1990-05-03 1991-11-14 E.I. Du Pont De Nemours And Company Improved process for the rapid production of cyclic esters
US5043458A (en) * 1990-05-03 1991-08-27 E. I. Du Pont De Nemours And Company One-step continuous process for preparing cyclic esters
US5023349A (en) * 1990-05-08 1991-06-11 E. I. Du Pont De Nemours And Company Continuous process for rapid conversion of oligomers to cyclic esters
US5097005A (en) * 1990-05-11 1992-03-17 E. I. Du Pont De Nemours And Company Novel copolyesters and their use in compostable products such as disposable diapers
US5023350A (en) * 1990-05-24 1991-06-11 E. I. Du Pont De Nemours And Company Process for the purification of cyclic esters
WO1992000292A1 (en) * 1990-06-28 1992-01-09 E.I. Du Pont De Nemours And Company Continuous catalyzed vapor phase dimeric cyclic ester process
WO1992000974A1 (en) * 1990-07-13 1992-01-23 E.I. Du Pont De Nemours And Company High yield recycle process for lactide
US5076983A (en) * 1990-07-16 1991-12-31 E. I. Du Pont De Nemours And Company Polyhydroxy acid films
US5134171A (en) * 1990-07-16 1992-07-28 E. I. Du Pont De Nemours And Company Degradable foam materials
WO1992004413A1 (en) * 1990-09-06 1992-03-19 Biopak Technology Ltd Packaging thermoplastics from lactic acid
WO1992004412A1 (en) * 1990-09-11 1992-03-19 E.I. Du Pont De Nemours And Company Films containing polyhydroxy acids
WO1992004410A1 (en) * 1990-09-11 1992-03-19 E.I. Du Pont De Nemours And Company Films containing polyhydroxy acids and a compatibilizer
WO1992005167A1 (en) * 1990-09-18 1992-04-02 Biopak Technology Ltd Lactide production from dehydration of aqueous lactic acid feed
WO1992005168A1 (en) * 1990-09-18 1992-04-02 Biopak Technology Ltd. Catalytic production of lactide directly from lactic acid
WO1992005311A1 (en) * 1990-09-26 1992-04-02 E.I. Du Pont De Nemours And Company Cellulosic pulp bonded by polyhydroxy acid resins
EP0481732A1 (en) * 1990-10-16 1992-04-22 Takeda Chemical Industries, Ltd. Prolonged release preparation and polymers thereof
US5136017A (en) * 1991-02-22 1992-08-04 Polysar Financial Services S.A. Continuous lactide polymerization
WO1992015340A1 (en) * 1991-03-04 1992-09-17 Guidor Ab Bioresorbable material and an article of manufacture made of such material for medical use
JPH04283227A (en) * 1991-03-11 1992-10-08 Mitsui Toatsu Chem Inc Hydrolyzable resin composition
EP0507554A1 (en) * 1991-04-01 1992-10-07 MITSUI TOATSU CHEMICALS, Inc. Degradable foam, process for its preparation and use of same
US5132397A (en) * 1991-04-02 1992-07-21 Polysar Financial Services S.A. 4-valerolactone copolymers
US5223546A (en) * 1991-04-24 1993-06-29 Mitsui Toatsu Chemicals, Inc. High polymer network
US5340646A (en) * 1991-04-26 1994-08-23 Mitsui Toatsu Chemicals, Inc. Breathable, hydrolyzable porous film
EP0510998A2 (en) * 1991-04-26 1992-10-28 MITSUI TOATSU CHEMICALS, Inc. Porous film
EP0515203A2 (en) * 1991-05-24 1992-11-25 Camelot Technologies Inc. Polylactide blends
US5296229A (en) * 1991-07-19 1994-03-22 Solvay (Societe Anonyme) Flexible, elastic and biodegradable film made of polymer based on lactic acid, capable of being suitable especially for the production of medical dressings
WO1993002075A1 (en) * 1991-07-24 1993-02-04 E.I. Du Pont De Nemours And Company Thin film depolymerization to dimeric cyclic esters
EP0532154A2 (en) * 1991-09-12 1993-03-17 Novacor Chemicals (International) S.A. Process for devolatilization of polylactides
EP0533314A2 (en) * 1991-09-17 1993-03-24 Novacor Chemicals (International) S.A. Biodegradable polyester compositions
US5142023A (en) * 1992-01-24 1992-08-25 Cargill, Incorporated Continuous process for manufacture of lactide polymers with controlled optical purity
US5338822A (en) * 1992-10-02 1994-08-16 Cargill, Incorporated Melt-stable lactide polymer composition and process for manufacture thereof

Non-Patent Citations (118)

* Cited by examiner, † Cited by third party
Title
"Argus Product Data, Argus® Dimyristyl Thiodipropionate", (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231-2193).
"Argus Product Data, Argus® Distearyl Thiodipropionate", (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231-2193).
"Argus Product Data, Mark® 2140 Pentaerythrityl Octylthiopropionate", (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231-2193).
"Argus Product Data, Seenox® 412S Pentaerythritol Tetrakas (B-Laurylthiopropionate)", (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231-2193).
"Argus Thiochemical Product Data, Argus® Dilauryl Thiodipropionate", (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231-2193).
"Argus Thiochemical Product Data, Argus® Thiodipropionate", (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231-2193).
"Biocompatible Composite Would Be Completely Absorbed in the Body", Advanced Materials, vol. 12, No. 15, Aug. 1990, p.6.
"Ethanox® 398 Antioxidant, The First Fluorophosphonite Antioxidant", (published on or before an unknown date in Oct., 1990, by Ethyl Corporation, 451 Florida Blvd., Baton Rouge, LA 70801).
"GE Specialty Chemicals Product Guide CA-4001E", (published on an unknown date in 1989, by General Electric Company, 5th and Avery Street, Parkersburg, WV 26102).
"Hydrolytic Stability/Corrosivity of Phosphite Costabilizers", (Technical Bulletin 89-04, published on an unknown date in 1989, by Stars Laboratory, Additives Division, Ciba-Geigy Corporation, Ardsley, NY 10502).
"Irganox® 1010", (a product brochure published on or before an unknown date in Aug., 1992, by Ciba-Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532).
"Irganox® 1076 Antioxidant and Thermal Stabilizer", (published on an unknown date in 1986 by Ciba-Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532).
"Irganox® B-Blends Antioxidants and Process Stabilizers for Polymers", (published on an unknown date in Mar. 1990, by Ciba-Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532).
"Irganox®MD 1024, Metal Deactivator/Antioxidant", (published on an unknown date prior to Aug., 1992, by Ciba-Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532).
"Naugard® 445, Specialty Chemicals", (a product brochure published on or before May 1, 1990, by Uniroyal Chemical Company, Inc., Middlebury, CT 06749).
"Naugard® XL-1 Specialty Chemicals", (product brochure published on an unknown date in Feb., 1992, by Uniroyal Chemical Co., Inc., Middlebury, CT 06749).
"Polylactides Exhibit Degradability", Tappi Journal, Sep. 1991, p. 42.
"The Resomer® Resorbable Polyesters" (published on or before an unknown date in Feb., 1991 by Boehringer Ingelheim KG, D-6507 Ingelheim, W. Germany).
"Tinuvin® 123 Hindered Aminoether Light Stabilizer for Coatings", (published on an unknown date in 1989, by Ciba-Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532).
"Tinuvin® 622LD Low Dust, Hindered Amine Light Stabilizer for Polymers FDA-Cleared for Polyolefins", (published on an unknown date before Aug., 1992, by Ciba-Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532).
A. Chawla and T. Chang ( In Vivo Degradation of Poly(lactic acid) of Different Molecular Weights , Nov. 1985, Biomat., Med. Dev., Art. Org. , v. 13, pp. 153 162). *
A. Chawla and T. Chang ("In-Vivo Degradation of Poly(lactic acid) of Different Molecular Weights", Nov. 1985, Biomat., Med. Dev., Art. Org., v. 13, pp. 153-162).
A. D. Schwope et al., "Lactic/Glycolic Acid Polymers as Narcotic Antagonist Delivery Systems", Life Sciences, vol. 17, 1877-1886 May (1975).
A. D. Schwope et al., Lactic/Glycolic Acid Polymers as Narcotic Antagonist Delivery Systems , Life Sciences , vol. 17, 1877 1886 May (1975). *
A. M. Reed and D. K. Gilding, "Biodegradable Polymers for Use in Surgery Polyglycolic/Polylactic Acid Homo and Copolymers: 2. In Vitro Degradation", Polymer, vol. 22, No. 4, 494-498 Apr. (1981).
A. M. Reed and D. K. Gilding, Biodegradable Polymers for Use in Surgery Polyglycolic/Polylactic Acid Homo and Copolymers: 2. In Vitro Degradation , Polymer , vol. 22, No. 4, 494 498 Apr. (1981). *
A. Schindler, R. Jeffcoat, G. Kimmel, C. Pitt, M. Wall and R. Zweidinnger ( Biodegradable Polymers for Sustained Drug Delivery , Aug. 1977, Contemporary Topics in Polymer Science , v. 2, pp. 251 287). *
A. Schindler, R. Jeffcoat, G. Kimmel, C. Pitt, M. Wall and R. Zweidinnger ("Biodegradable Polymers for Sustained Drug Delivery", Aug. 1977, Contemporary Topics in Polymer Science, v. 2, pp. 251-287).
Argus Product Data, Argus Dimyristyl Thiodipropionate , (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231 2193). *
Argus Product Data, Argus Distearyl Thiodipropionate , (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231 2193). *
Argus Product Data, Mark 2140 Pentaerythrityl Octylthiopropionate , (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231 2193). *
Argus Product Data, Seenox 412S Pentaerythritol Tetrakas (B Laurylthiopropionate) , (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231 2193). *
Argus Thiochemical Product Data, Argus Dilauryl Thiodipropionate , (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231 2193). *
Argus Thiochemical Product Data, Argus Thiodipropionate , (published on or before an unknown date in Aug., 1992, by Argus Division, Witco Corporation, 633 Court Street, Brooklyn, NY 11231 2193). *
Biocompatible Composite Would Be Completely Absorbed in the Body , Advanced Materials , vol. 12, No. 15, Aug. 1990, p.6. *
D. Deane and E. Hammond ( Coagulation of Milk for Cheese Making by Ester Hydrolysis , Jun. 1960, Journal of Dairy Science , v. 43, pp. 1421 1429). *
D. Deane and E. Hammond ("Coagulation of Milk for Cheese-Making by Ester Hydrolysis", Jun. 1960, Journal of Dairy Science, v. 43, pp. 1421-1429).
D. Garozzo, M. Giuffrida and G. Montaudo ( Primary Thermal Decomposition Processes in Aliphatic Polyesters Investigated by Chemical Ionization Mass Spectrometry , Apr. 1986, Macromolecules , v. 19, pp. 1643 1649). *
D. Garozzo, M. Giuffrida and G. Montaudo ("Primary Thermal Decomposition Processes in Aliphatic Polyesters Investigated by Chemical Ionization Mass Spectrometry", Apr. 1986, Macromolecules, v. 19, pp. 1643-1649).
D. K. Gilding et al., "Biodegradable Polymers for Use in Surgery--Polyglycolic/Polylactic Acid Homo and Copolymers: 1." Polymer, vol. 2, 1459-1464 Dec. (1979).
D. K. Gilding et al., Biodegradable Polymers for Use in Surgery Polyglycolic/Polylactic Acid Homo and Copolymers: 1. Polymer , vol. 2, 1459 1464 Dec. (1979). *
D. K. Gilding, "Biodegradable Polymers", Biocompatibility of Clinical Implant Materials, D. F. Williams, ed., vol. 2, 209-232 Feb. (1981).
D. K. Gilding, "Degradation of Polymers: Mechanisms and Implications for Biomedical Applications", Biocompatibility of Clinical Implant Materials, D. F. Williams, ed., vol. 1, 43-65 Aug. (1981).
D. K. Gilding, Biodegradable Polymers , Biocompatibility of Clinical Implant Materials , D. F. Williams, ed., vol. 2, 209 232 Feb. (1981). *
D. K. Gilding, Degradation of Polymers: Mechanisms and Implications for Biomedical Applications , Biocompatibility of Clinical Implant Materials , D. F. Williams, ed., vol. 1, 43 65 Aug. (1981). *
D. L. Wise et al., "Sustained Release of an Antimalarial Drug Using a Copolymer of Glycolic/Lactic Acid", Life Sciences, vol. 19, 867-874 Aug. (1976).
D. L. Wise et al., Sustained Release of an Antimalarial Drug Using a Copolymer of Glycolic/Lactic Acid , Life Sciences , vol. 19, 867 874 Aug. (1976). *
E. Filachione, E. Costello, T. Dietz and C. Fisher ( Lactic Acid Derivatives as Plasticizers Esters of Polymeric Lactic Acid , Jul. 1951, Bur. Agric. Ind. Chem. , v. 11, pp. 1 11). *
E. Filachione, E. Costello, T. Dietz and C. Fisher ("Lactic Acid Derivatives as Plasticizers Esters of Polymeric Lactic Acid", Jul. 1951, Bur. Agric. Ind. Chem., v. 11, pp. 1-11).
Ethanox 398 Antioxidant, The First Fluorophosphonite Antioxidant , (published on or before an unknown date in Oct., 1990, by Ethyl Corporation, 451 Florida Blvd., Baton Rouge, LA 70801). *
F. Chabot, M. Vert, S. Chapelle and P. Granger ( Configurational Structures of Lactic Acid Stereocopolymers as Determined by 13 C( 1 H) N.M.R. , Jul. 1983, Polymer , v. 24, pp. 53 59). *
F. Chabot, M. Vert, S. Chapelle and P. Granger ("Configurational Structures of Lactic Acid Stereocopolymers as Determined by 13 C(1 H) N.M.R.", Jul. 1983, Polymer, v. 24, pp. 53-59).
F. Kohn, J. Van Don Berg, G. Van De Ridder and J. Feijen ( The Ring Opening Polymerization of D,L Lactide in the Melt Initiated with Tetraphenyltin , Sep. 1984, Journal of Applied Polymer Science , v. 29, pp. 4265 4277). *
F. Kohn, J. Van Don Berg, G. Van De Ridder and J. Feijen ("The Ring-Opening Polymerization of D,L-Lactide in the Melt Initiated with Tetraphenyltin", Sep. 1984, Journal of Applied Polymer Science, v. 29, pp. 4265-4277).
G. Van Hummel and S. Harkema ( Structure of 3,6 Dimethyl 1,4 Dioxane 2,5 Dione D ,D L ,L Lactide , Jun. 1982, Acta. Crystallogr. , v. B38, pp. 1679 1681). *
G. Van Hummel and S. Harkema ("Structure of 3,6-Dimethyl-1,4-Dioxane-2,5-Dione [D-,D-{L-,L-}Lactide]", Jun. 1982, Acta. Crystallogr., v. B38, pp. 1679-1681).
GE Specialty Chemicals Product Guide CA 4001E , (published on an unknown date in 1989, by General Electric Company, 5th and Avery Street, Parkersburg, WV 26102). *
H. Kricheldorf and A. Serra ( Polylactones 6. Influence of Various Metal Salts on the Optical Purity of Poly(L lactide) , Aug. 1985, Polymer Bulletin , v. 14, pp. 497 502). *
H. Kricheldorf and A. Serra ("Polylactones 6. Influence of Various Metal Salts on the Optical Purity of Poly(L-lactide)", Aug. 1985, Polymer Bulletin, v. 14, pp. 497-502).
H. Kricheldorf, M. Berl and N. Scharnagl ( Polymerization Mechanism of Metal Alkoxide Initiated Polymerizations of Lactide and Various Lactones , Jan. 1988, Makromol. , v. 21, pp. 286 293). *
H. Kricheldorf, M. Berl and N. Scharnagl ("Polymerization Mechanism of Metal Alkoxide Initiated Polymerizations of Lactide and Various Lactones", Jan. 1988, Makromol., v. 21, pp. 286-293).
Hydrolytic Stability/Corrosivity of Phosphite Costabilizers , (Technical Bulletin 89 04, published on an unknown date in 1989, by Stars Laboratory, Additives Division, Ciba Geigy Corporation, Ardsley, NY 10502). *
I. Luderwald ( Thermal Degradation of Polyesters in the Mass Spectrometer , Dec. 1979, Dev. Polymer Degradation , v. 2, pp. 77 98). *
I. Luderwald ("Thermal Degradation of Polyesters in the Mass Spectrometer", Dec. 1979, Dev. Polymer Degradation, v. 2, pp. 77-98).
I. McNeill and H. Leiper ( Degradation Studies of Some Polyesters and Polycarbonates 1. Polylactide: General Features of the Degradation Under Programmed Heating Conditions , Jun. 1985, Polymer Degradation and Stability , v. 11, pp. 267 285). *
I. McNeill and H. Leiper ( Degradation Studies of Some Polyesters and Polycarbonates 2. Polylactide: Degradation Under Isothermal Conditions, Thermal Degradation Mechanism and Photolysis of the Polymer , Aug. 1985, Polymer Degradation and Stability , v. 11, pp. 309 326). *
I. McNeill and H. Leiper ("Degradation Studies of Some Polyesters and Polycarbonates--1. Polylactide: General Features of the Degradation Under Programmed Heating Conditions", Jun. 1985, Polymer Degradation and Stability, v. 11, pp. 267-285).
I. McNeill and H. Leiper ("Degradation Studies of Some Polyesters and Polycarbonates--2. Polylactide: Degradation Under Isothermal Conditions, Thermal Degradation Mechanism and Photolysis of the Polymer", Aug. 1985, Polymer Degradation and Stability, v. 11, pp. 309-326).
Irganox 1010 , (a product brochure published on or before an unknown date in Aug., 1992, by Ciba Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532). *
Irganox 1076 Antioxidant and Thermal Stabilizer , (published on an unknown date in 1986 by Ciba Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532). *
Irganox B Blends Antioxidants and Process Stabilizers for Polymers , (published on an unknown date in Mar. 1990, by Ciba Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532). *
Irganox MD 1024, Metal Deactivator/Antioxidant , (published on an unknown date prior to Aug., 1992, by Ciba Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532). *
J. D. Strobel, "Biodegradable Polymers", paper presented at Medical Textiles and Biomedical Polymers and Materials Conference held at Clemson, S.C., U.S.A., Dec. 5-6, 1989, Stolle Research and Development Corp., PD 712-01, pp. 1-32 and Attachments A1-A21.
J. D. Strobel, Biodegradable Polymers , paper presented at Medical Textiles and Biomedical Polymers and Materials Conference held at Clemson, S.C., U.S.A., Dec. 5 6, 1989, Stolle Research and Development Corp., PD 712 01, pp. 1 32 and Attachments A1 A21. *
J. Leenslag and A. Pennings ( Synthesis of high molecular weight poly(L lactide) initiated with tin 2 ethylhexanoate , Apr. 1987, Makromol. Chem. , v. 188, pp. 1809 1814). *
J. Leenslag and A. Pennings ( Synthesis of high molecular weight poly(L lactide) initiated with tin 2 ethylhexanoate , May 1987, Makromol. Chem. , v. 188, pp. 1809 1814). *
J. Leenslag and A. Pennings ("Synthesis of high-molecular-weight poly(L-lactide) initiated with tin 2-ethylhexanoate", Apr. 1987, Makromol. Chem., v. 188, pp. 1809-1814).
J. Leenslag and A. Pennings ("Synthesis of high-molecular-weight poly(L-lactide) initiated with tin 2-ethylhexanoate", May 1987, Makromol. Chem., v. 188, pp. 1809-1814).
K. Jamshidi, S. Hyon and Y. Ikada ( Thermal Characterization of Polylactides , Feb. 1988, Polymer , v. 29, pp. 2229 2234). *
K. Jamshidi, S. Hyon and Y. Ikada ("Thermal Characterization of Polylactides", Feb. 1988, Polymer, v. 29, pp. 2229-2234).
Kulkarni et al. ( Biodegradable Poly(lactic acid) Polymers , May 1971, J. Biomed. Mater. Res. , v. 5, pp. 169 181). *
Kulkarni et al. ("Biodegradable Poly(lactic acid) Polymers", May 1971, J. Biomed. Mater. Res., v. 5, pp. 169-181).
L. C. Anderson, "An Injectable Sustained Release Fertility Control System", Contraception, vol. 13, No. 3, 375-384 Jun. (1976).
L. C. Anderson, An Injectable Sustained Release Fertility Control System , Contraception , vol. 13, No. 3, 375 384 Jun. (1976). *
M. Gupta and V. Deshmukh ( Thermal Oxidative Degradation of Poly lactic Acid; Part I: Activation Energy of Thermal Degradation in Air , Apr. 1982, Colloid & Polymer Science , v. 260, pp. 308 311). *
M. Gupta and V. Deshmukh ( Thermal Oxidative Degradation of Poly lactic Acid; Part II: Molecular Weight and Electronic Spectra During Isothermal Heating , Mar. 1982, Colloid & Polymer Science , v. 260, pp. 514 517). *
M. Gupta and V. Deshmukh ("Thermal Oxidative Degradation of Poly-lactic Acid; Part I: Activation Energy of Thermal Degradation in Air", Apr. 1982, Colloid & Polymer Science, v. 260, pp. 308-311).
M. Gupta and V. Deshmukh ("Thermal Oxidative Degradation of Poly-lactic Acid; Part II: Molecular Weight and Electronic Spectra During Isothermal Heating", Mar. 1982, Colloid & Polymer Science, v. 260, pp. 514-517).
M. Vert ( Bioresorbable Polymers for Temporary Therapeutic Applications , Mar. 1989, Die Angwandte Makromolekulare Chemie , v. 166 167, pp. 155 168). *
M. Vert ("Bioresorbable Polymers for Temporary Therapeutic Applications", Mar. 1989, Die Angwandte Makromolekulare Chemie, v. 166-167, pp. 155-168).
M. Vert and F. Chabot ( Stereoregular Bioresorbable Polyesters for Orthopaedic Surgery , Aug. 1981, Makromol. Chem. , Supp. 5, pp. 30 41). *
M. Vert and F. Chabot ("Stereoregular Bioresorbable Polyesters for Orthopaedic Surgery", Aug. 1981, Makromol. Chem., Supp. 5, pp. 30-41).
Makino et al. ( Preparation and in Vitro Degradation Properties of Polylactide Microcapsules , Feb. 1985, Chem. Pharm. Bull. , v. 33, pp. 1195 1201). *
Makino et al. ("Preparation and in Vitro Degradation Properties of Polylactide Microcapsules", Feb. 1985, Chem. Pharm. Bull., v. 33, pp. 1195-1201).
Nakamura et al. ( Surgical Application of Biodegradable Films Prepared from Lactide Caprolactone Copolymers , Jun. 1987, Bio. Materials and Clinical Applications , v. 7, pp. 759 764). *
Nakamura et al. ("Surgical Application of Biodegradable Films Prepared from Lactide-ε-Caprolactone Copolymers", Jun. 1987, Bio. Materials and Clinical Applications, v. 7, pp. 759-764).
Naugard 445, Specialty Chemicals , (a product brochure published on or before May 1, 1990, by Uniroyal Chemical Company, Inc., Middlebury, CT 06749). *
Naugard XL 1 Specialty Chemicals , (product brochure published on an unknown date in Feb., 1992, by Uniroyal Chemical Co., Inc., Middlebury, CT 06749). *
P. Klemchuk, ( Introduction to Polymer Degradation , lecture notes distributed at a seminar entitled: Principles of Polymer Degradation and Stabilization in Orlando, Florida, Oct. 28 30, 1991, sponsored by The Institute of Materials Science, State University of New York at New Paltz). *
P. Klemchuk, ("Introduction to Polymer Degradation", lecture notes distributed at a seminar entitled: Principles of Polymer Degradation and Stabilization in Orlando, Florida, Oct. 28-30, 1991, sponsored by The Institute of Materials Science, State University of New York at New Paltz).
P. V. Bonsignore et al., Nov. 1992, "Poly(lactic acid) Degradable Plastics, Coatings, and Binders", TAPPI Proceedings (Nonwovens Conference); pp. 129-140.
P. V. Bonsignore et al., Nov. 1992, Poly(lactic acid) Degradable Plastics, Coatings, and Binders , TAPPI Proceedings (Nonwovens Conference); pp. 129 140. *
Polylactides Exhibit Degradability , Tappi Journal , Sep. 1991, p. 42. *
R. A. Miller et al., "Degradation Rates of Resorbable Implants (Polylactates and Polyglycolates): Rate Modification with Changes in Pla/Pga Copolymer Rations", J. Biomed. Mater. Res., vol. 11, 711-719 Oct. (1977).
R. A. Miller et al., Degradation Rates of Resorbable Implants (Polylactates and Polyglycolates): Rate Modification with Changes in Pla/Pga Copolymer Rations , J. Biomed. Mater. Res. , vol. 11, 711 719 Oct. (1977). *
R. Thomas, ( Degradation and Stabilization of Engineering Polymers , lecture notes distributed at a seminar entitled: Principles of Polymer Degradation and Stabilization in Orlando, Florida, Oct. 28 30, 1991, sponsored by The Institute of Materials Science, State University of New York at New Paltz). *
R. Thomas, ("Degradation and Stabilization of Engineering Polymers", lecture notes distributed at a seminar entitled: Principles of Polymer Degradation and Stabilization in Orlando, Florida, Oct. 28-30, 1991, sponsored by The Institute of Materials Science, State University of New York at New Paltz).
Sir John Meurig Thomas, ( Solid Acid Catalysts , Apr. 1992, Scientific American , pp. 112 118). *
Sir John Meurig Thomas, ("Solid Acid Catalysts", Apr. 1992, Scientific American, pp. 112-118).
T. M. Jackanicz, "Polylactic Acid as a Biodegradable Carrier for Contraceptive Steroids", Contraception, vol. 8, No. 3, 227-234 Jan. (1973).
T. M. Jackanicz, Polylactic Acid as a Biodegradable Carrier for Contraceptive Steroids , Contraception , vol. 8, No. 3, 227 234 Jan. (1973). *
The Resomer Resorbable Polyesters (published on or before an unknown date in Feb., 1991 by Boehringer Ingelheim KG, D 6507 Ingelheim, W. Germany). *
Tinuvin 123 Hindered Aminoether Light Stabilizer for Coatings , (published on an unknown date in 1989, by Ciba Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532). *
Tinuvin 622LD Low Dust, Hindered Amine Light Stabilizer for Polymers FDA Cleared for Polyolefins , (published on an unknown date before Aug., 1992, by Ciba Geigy Corporation, Three Skyline Drive, Hawthorne, NY 10532). *
W. Carothers, G. Dorough, and F. Van Natta ( Studies of Polymerization and Ring Formation. X. The Reversible Polymerization of Six Membered Cyclic Esters , Jan. 1932, American Chemical Society Journal , v. 54, pp. 761 772). *
W. Carothers, G. Dorough, and F. Van Natta ("Studies of Polymerization and Ring Formation. X. The Reversible Polymerization of Six-Membered Cyclic Esters", Jan. 1932, American Chemical Society Journal, v. 54, pp. 761-772).
W. Enlow, ( Process Stabilization with Phosphite Antioxidants , lecture notes distributed at a seminar entitled: Principles of Polymer Degradation and Stabilization in Orlando, Florida, Oct. 28 30, 1991, sponsored by The Institute of Materials Science, State University of New York at New Paltz). *
W. Enlow, ("Process Stabilization with Phosphite Antioxidants", lecture notes distributed at a seminar entitled: Principles of Polymer Degradation and Stabilization in Orlando, Florida, Oct. 28-30, 1991, sponsored by The Institute of Materials Science, State University of New York at New Paltz).

Cited By (193)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6093791A (en) * 1992-10-02 2000-07-25 Cargill, Incorporated Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
US6121410A (en) * 1992-10-02 2000-09-19 Cargill, Incorporated Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
US5773562A (en) * 1992-10-02 1998-06-30 Cargill, Incorporated Melt-stable semi-crystalline lactide polymer film and process for manufacture thereof
US5866634A (en) * 1995-09-25 1999-02-02 Shin-Etsu Chemical Co., Ltd Biodegradable polymer compositions and shrink films
US5849374A (en) * 1995-09-28 1998-12-15 Cargill, Incorporated Compostable multilayer structures, methods for manufacture, and articles prepared therefrom
US5849401A (en) * 1995-09-28 1998-12-15 Cargill, Incorporated Compostable multilayer structures, methods for manufacture, and articles prepared therefrom
US6312823B1 (en) 1995-09-28 2001-11-06 Cargrill, Incorporated Compostable multilayer structures, methods for manufacture and articles prepared therefrom
US5895587A (en) * 1997-01-21 1999-04-20 Cryovac, Inc. Cook-in package and method of making same
US6506873B1 (en) 1997-05-02 2003-01-14 Cargill, Incorporated Degradable polymer fibers; preparation product; and, methods of use
US6183814B1 (en) 1997-05-23 2001-02-06 Cargill, Incorporated Coating grade polylactide and coated paper, preparation and uses thereof, and articles prepared therefrom
US7070795B1 (en) 1997-06-30 2006-07-04 Monsanto Company Particles containing agricultural active ingredients
US7452546B2 (en) 1997-06-30 2008-11-18 Monsanto Technology Llc Particles containing agricultural active ingredients
US20060193882A1 (en) * 1997-06-30 2006-08-31 Monsanto Technology, L.L.C. Particles containing agricultural active ingredients
US20060094093A1 (en) * 1997-10-14 2006-05-04 Cargill, Inc Low pH lactic acid fermentation
US6475759B1 (en) 1997-10-14 2002-11-05 Cargill, Inc. Low PH lactic acid fermentation
US6534679B2 (en) 1997-10-14 2003-03-18 Cargill, Incorporated Lactic acid processing; methods; arrangements; and, products
US20030129715A1 (en) * 1997-10-14 2003-07-10 Cargill, Inc. Low pH lactic acid fermentation
EP1930408A2 (en) 1997-10-14 2008-06-11 Cargill Incorporated Acid-tolerant homolactic bacteria
US6320077B1 (en) 1997-10-14 2001-11-20 Cargill, Incorporated Lactic acid processing; methods; arrangements; and, product
US7144977B2 (en) 1997-10-14 2006-12-05 Cargill, Incorporated Lactic acid processing; methods; arrangements; and, products
US20040210088A1 (en) * 1997-10-14 2004-10-21 Cargill, Incorporated Lactic acid processing; methods; arrangements; and, products
US6229046B1 (en) 1997-10-14 2001-05-08 Cargill, Incorported Lactic acid processing methods arrangements and products
US6353086B1 (en) 1998-04-01 2002-03-05 Cargill, Incorporated Lactic acid residue containing polymer composition and product having improved stability, and method for preparation and use thereof
US6114495A (en) * 1998-04-01 2000-09-05 Cargill Incorporated Lactic acid residue containing polymer composition and product having improved stability, and method for preparation and use thereof
US6672001B1 (en) * 1998-11-17 2004-01-06 Board Of Regents Of University Of Nebraska Method for mulching an agricultural soil bed using a biodegradable protein material, and a mulched agricultural crop growing plot produced thereby
US6123811A (en) * 1998-12-14 2000-09-26 Ethicon, Inc. Method of manufacturing aqueous paper pulp for water soluble packages
US20040209073A1 (en) * 2001-06-06 2004-10-21 Sonja Rosenbaum Biodegradable biaxially drawn film with controlled tear resistance
US20040214724A1 (en) * 2001-06-11 2004-10-28 Todd Bradley L. Compositions and methods for reducing the viscosity of a fluid
US7168489B2 (en) 2001-06-11 2007-01-30 Halliburton Energy Services, Inc. Orthoester compositions and methods for reducing the viscosified treatment fluids
US20050045328A1 (en) * 2001-06-11 2005-03-03 Frost Keith A. Orthoester compositions and methods for reducing the viscosified treatment fluids
US7276466B2 (en) 2001-06-11 2007-10-02 Halliburton Energy Services, Inc. Compositions and methods for reducing the viscosity of a fluid
US7175917B2 (en) * 2001-11-01 2007-02-13 Asahi Kasei Life & Living Corporation Biaxially oriented polylactic acid-based resin films
US20050008815A1 (en) * 2001-11-01 2005-01-13 Masayuki Sukigara Biaxially oriented polylactic acid-based resin films
US8354279B2 (en) 2002-04-18 2013-01-15 Halliburton Energy Services, Inc. Methods of tracking fluids produced from various zones in a subterranean well
US7300787B2 (en) 2002-07-05 2007-11-27 Archer-Daniels-Midland Company Lactobacillus strains and use thereof in fermentation for L-lactic acid production
US20040005677A1 (en) * 2002-07-05 2004-01-08 Eddington John M. Novel lactobacillus strains and use thereof in fermentation process for L-lactic acid production
US20040176513A1 (en) * 2002-10-24 2004-09-09 Mukerrem Cakmak Process for making strain-hardened polymer products
US7714054B2 (en) * 2002-10-24 2010-05-11 The University Of Akron Process for making strain-hardened polymer products
US7178596B2 (en) 2003-06-27 2007-02-20 Halliburton Energy Services, Inc. Methods for improving proppant pack permeability and fracture conductivity in a subterranean well
US7044224B2 (en) 2003-06-27 2006-05-16 Halliburton Energy Services, Inc. Permeable cement and methods of fracturing utilizing permeable cement in subterranean well bores
US20040261993A1 (en) * 2003-06-27 2004-12-30 Nguyen Philip D. Permeable cement and sand control methods utilizing permeable cement in subterranean well bores
US20040261999A1 (en) * 2003-06-27 2004-12-30 Nguyen Philip D. Permeable cement and methods of fracturing utilizing permeable cement in subterranean well bores
US20040261996A1 (en) * 2003-06-27 2004-12-30 Trinidad Munoz Methods of diverting treating fluids in subterranean zones and degradable diverting materials
US20040261995A1 (en) * 2003-06-27 2004-12-30 Nguyen Philip D. Compositions and methods for improving proppant pack permeability and fracture conductivity in a subterranean well
US7228904B2 (en) 2003-06-27 2007-06-12 Halliburton Energy Services, Inc. Compositions and methods for improving fracture conductivity in a subterranean well
US20050059558A1 (en) * 2003-06-27 2005-03-17 Blauch Matthew E. Methods for improving proppant pack permeability and fracture conductivity in a subterranean well
US20050126780A1 (en) * 2003-06-27 2005-06-16 Halliburton Energy Services, Inc. Compositions and methods for improving fracture conductivity in a subterranean well
US7032663B2 (en) 2003-06-27 2006-04-25 Halliburton Energy Services, Inc. Permeable cement and sand control methods utilizing permeable cement in subterranean well bores
US7044220B2 (en) 2003-06-27 2006-05-16 Halliburton Energy Services, Inc. Compositions and methods for improving proppant pack permeability and fracture conductivity in a subterranean well
US7036587B2 (en) 2003-06-27 2006-05-02 Halliburton Energy Services, Inc. Methods of diverting treating fluids in subterranean zones and degradable diverting materials
US20050028976A1 (en) * 2003-08-05 2005-02-10 Nguyen Philip D. Compositions and methods for controlling the release of chemicals placed on particulates
US7140438B2 (en) 2003-08-14 2006-11-28 Halliburton Energy Services, Inc. Orthoester compositions and methods of use in subterranean applications
US20050034868A1 (en) * 2003-08-14 2005-02-17 Frost Keith A. Orthoester compositions and methods of use in subterranean applications
US20050034865A1 (en) * 2003-08-14 2005-02-17 Todd Bradley L. Compositions and methods for degrading filter cake
US7080688B2 (en) 2003-08-14 2006-07-25 Halliburton Energy Services, Inc. Compositions and methods for degrading filter cake
US8541051B2 (en) 2003-08-14 2013-09-24 Halliburton Energy Services, Inc. On-the fly coating of acid-releasing degradable material onto a particulate
US7497278B2 (en) 2003-08-14 2009-03-03 Halliburton Energy Services, Inc. Methods of degrading filter cakes in a subterranean formation
US6997259B2 (en) 2003-09-05 2006-02-14 Halliburton Energy Services, Inc. Methods for forming a permeable and stable mass in a subterranean formation
US20050056423A1 (en) * 2003-09-11 2005-03-17 Todd Bradey L. Methods of removing filter cake from well producing zones
US7021377B2 (en) 2003-09-11 2006-04-04 Halliburton Energy Services, Inc. Methods of removing filter cake from well producing zones
US20050059556A1 (en) * 2003-09-17 2005-03-17 Trinidad Munoz Treatment fluids and methods of use in subterranean formations
US7674753B2 (en) 2003-09-17 2010-03-09 Halliburton Energy Services, Inc. Treatment fluids and methods of forming degradable filter cakes comprising aliphatic polyester and their use in subterranean formations
US7833944B2 (en) 2003-09-17 2010-11-16 Halliburton Energy Services, Inc. Methods and compositions using crosslinked aliphatic polyesters in well bore applications
US7829507B2 (en) 2003-09-17 2010-11-09 Halliburton Energy Services Inc. Subterranean treatment fluids comprising a degradable bridging agent and methods of treating subterranean formations
US7598208B2 (en) 2003-12-15 2009-10-06 Halliburton Energy Services, Inc. Filter cake degradation compositions and methods of use in subterranean operations
US7195068B2 (en) 2003-12-15 2007-03-27 Halliburton Energy Services, Inc. Filter cake degradation compositions and methods of use in subterranean operations
US20050126785A1 (en) * 2003-12-15 2005-06-16 Todd Bradley L. Filter cake degradation compositions and methods of use in subterranean operations
US7096947B2 (en) 2004-01-27 2006-08-29 Halliburton Energy Services, Inc. Fluid loss control additives for use in fracturing subterranean formations
US20050161220A1 (en) * 2004-01-27 2005-07-28 Todd Bradley L. Fluid loss control additives for use in fracturing subterranean formations
US7204312B2 (en) 2004-01-30 2007-04-17 Halliburton Energy Services, Inc. Compositions and methods for the delivery of chemical components in subterranean well bores
US20050167104A1 (en) * 2004-01-30 2005-08-04 Roddy Craig W. Compositions and methods for the delivery of chemical components in subterranean well bores
US20050167107A1 (en) * 2004-01-30 2005-08-04 Roddy Craig W. Methods of cementing in subterranean formations using crack resistant cement compositions
US7156174B2 (en) 2004-01-30 2007-01-02 Halliburton Energy Services, Inc. Contained micro-particles for use in well bore operations
US20050167105A1 (en) * 2004-01-30 2005-08-04 Roddy Craig W. Contained micro-particles for use in well bore operations
US7036586B2 (en) 2004-01-30 2006-05-02 Halliburton Energy Services, Inc. Methods of cementing in subterranean formations using crack resistant cement compositions
US7963330B2 (en) 2004-02-10 2011-06-21 Halliburton Energy Services, Inc. Resin compositions and methods of using resin compositions to control proppant flow-back
US7326659B2 (en) 2004-02-16 2008-02-05 Conwed Plastics Llc Biodegradable netting
US20050183329A1 (en) * 2004-02-16 2005-08-25 Cederblad Hans O. Biodegradable netting
US8017561B2 (en) 2004-03-03 2011-09-13 Halliburton Energy Services, Inc. Resin compositions and methods of using such resin compositions in subterranean applications
US20070100029A1 (en) * 2004-03-17 2007-05-03 Reddy B R Cement compositions containing degradable materials and methods of cementing in subterranean formations
US20050205258A1 (en) * 2004-03-17 2005-09-22 Reddy B R Cement compositions containing degradable materials and methods of cementing in subterranean formations
US7172022B2 (en) 2004-03-17 2007-02-06 Halliburton Energy Services, Inc. Cement compositions containing degradable materials and methods of cementing in subterranean formations
US7712531B2 (en) 2004-06-08 2010-05-11 Halliburton Energy Services, Inc. Methods for controlling particulate migration
US7475728B2 (en) 2004-07-23 2009-01-13 Halliburton Energy Services, Inc. Treatment fluids and methods of use in subterranean formations
US7299869B2 (en) 2004-09-03 2007-11-27 Halliburton Energy Services, Inc. Carbon foam particulates and methods of using carbon foam particulates in subterranean applications
US20060048938A1 (en) * 2004-09-03 2006-03-09 Kalman Mark D Carbon foam particulates and methods of using carbon foam particulates in subterranean applications
US7413017B2 (en) 2004-09-24 2008-08-19 Halliburton Energy Services, Inc. Methods and compositions for inducing tip screenouts in frac-packing operations
US7757768B2 (en) 2004-10-08 2010-07-20 Halliburton Energy Services, Inc. Method and composition for enhancing coverage and displacement of treatment fluids into subterranean formations
US7938181B2 (en) 2004-10-08 2011-05-10 Halliburton Energy Services, Inc. Method and composition for enhancing coverage and displacement of treatment fluids into subterranean formations
US7553800B2 (en) 2004-11-17 2009-06-30 Halliburton Energy Services, Inc. In-situ filter cake degradation compositions and methods of use in subterranean formations
US7648946B2 (en) 2004-11-17 2010-01-19 Halliburton Energy Services, Inc. Methods of degrading filter cakes in subterranean formations
US7883740B2 (en) 2004-12-12 2011-02-08 Halliburton Energy Services, Inc. Low-quality particulates and methods of making and using improved low-quality particulates
US8030249B2 (en) 2005-01-28 2011-10-04 Halliburton Energy Services, Inc. Methods and compositions relating to the hydrolysis of water-hydrolysable materials
US8030251B2 (en) 2005-01-28 2011-10-04 Halliburton Energy Services, Inc. Methods and compositions relating to the hydrolysis of water-hydrolysable materials
US7267170B2 (en) 2005-01-31 2007-09-11 Halliburton Energy Services, Inc. Self-degrading fibers and associated methods of use and manufacture
US20060169449A1 (en) * 2005-01-31 2006-08-03 Halliburton Energy Services, Inc. Self-degrading fibers and associated methods of use and manufacture
US8188013B2 (en) 2005-01-31 2012-05-29 Halliburton Energy Services, Inc. Self-degrading fibers and associated methods of use and manufacture
US7353876B2 (en) 2005-02-01 2008-04-08 Halliburton Energy Services, Inc. Self-degrading cement compositions and methods of using self-degrading cement compositions in subterranean formations
US20060169453A1 (en) * 2005-02-01 2006-08-03 Savery Mark R Kickoff plugs comprising a self-degrading cement in subterranean well bores
US8598092B2 (en) 2005-02-02 2013-12-03 Halliburton Energy Services, Inc. Methods of preparing degradable materials and methods of use in subterranean formations
US20060185847A1 (en) * 2005-02-22 2006-08-24 Halliburton Energy Services, Inc. Methods of placing treatment chemicals
US7216705B2 (en) 2005-02-22 2007-05-15 Halliburton Energy Services, Inc. Methods of placing treatment chemicals
US7506689B2 (en) 2005-02-22 2009-03-24 Halliburton Energy Services, Inc. Fracturing fluids comprising degradable diverting agents and methods of use in subterranean formations
US7673686B2 (en) 2005-03-29 2010-03-09 Halliburton Energy Services, Inc. Method of stabilizing unconsolidated formation for sand control
US20090074999A1 (en) * 2005-05-11 2009-03-19 Takashi Hiruma Heat-shrinkable film, moldings and heat-shrinkable labels made using the heat-shrinkable film, and containers made by using the moldings or fitted with the labels
US8470420B2 (en) 2005-05-11 2013-06-25 Mitsubishi Plastics, Inc. Heat-shrinkable film, moldings and heat-shrinkable labels made using the heat-shrinkable film, and containers made by using the moldings or fitted with the labels
US7677315B2 (en) 2005-05-12 2010-03-16 Halliburton Energy Services, Inc. Degradable surfactants and methods for use
US7662753B2 (en) 2005-05-12 2010-02-16 Halliburton Energy Services, Inc. Degradable surfactants and methods for use
US8689872B2 (en) 2005-07-11 2014-04-08 Halliburton Energy Services, Inc. Methods and compositions for controlling formation fines and reducing proppant flow-back
US7700525B2 (en) 2005-09-22 2010-04-20 Halliburton Energy Services, Inc. Orthoester-based surfactants and associated methods
US7713916B2 (en) 2005-09-22 2010-05-11 Halliburton Energy Services, Inc. Orthoester-based surfactants and associated methods
US20080311320A1 (en) * 2005-11-30 2008-12-18 Mitsubishi Plastics , Inc. Polyolefin Series Heat-Shrinkable Film, Molded Product and Heat-Shrinkable Laminated Label Employing the Film, and Container
US8137773B2 (en) * 2005-11-30 2012-03-20 Mitsubishi Plastics, Inc. Polyolefin series heat-shrinkable film, molded product and heat-shrinkable laminated label employing the film, and container
US8613320B2 (en) 2006-02-10 2013-12-24 Halliburton Energy Services, Inc. Compositions and applications of resins in treating subterranean formations
US7926591B2 (en) 2006-02-10 2011-04-19 Halliburton Energy Services, Inc. Aqueous-based emulsified consolidating agents suitable for use in drill-in applications
US8443885B2 (en) 2006-02-10 2013-05-21 Halliburton Energy Services, Inc. Consolidating agent emulsions and associated methods
US7819192B2 (en) 2006-02-10 2010-10-26 Halliburton Energy Services, Inc. Consolidating agent emulsions and associated methods
US20070289781A1 (en) * 2006-02-10 2007-12-20 Halliburton Energy Services, Inc. Consolidating agent emulsions and associated methods
US7665517B2 (en) 2006-02-15 2010-02-23 Halliburton Energy Services, Inc. Methods of cleaning sand control screens and gravel packs
US7608566B2 (en) 2006-03-30 2009-10-27 Halliburton Energy Services, Inc. Degradable particulates as friction reducers for the flow of solid particulates and associated methods of use
US7237610B1 (en) 2006-03-30 2007-07-03 Halliburton Energy Services, Inc. Degradable particulates as friction reducers for the flow of solid particulates and associated methods of use
US20080076696A1 (en) * 2006-06-21 2008-03-27 David Uitenbrock Dryer sheet and methods for manufacturing and using a dryer sheet
US7943566B2 (en) 2006-06-21 2011-05-17 Wausau Paper Mills, Llc Dryer sheet and methods for manufacturing and using a dryer sheet
US20080006406A1 (en) * 2006-07-06 2008-01-10 Halliburton Energy Services, Inc. Methods of enhancing uniform placement of a resin in a subterranean formation
US9173973B2 (en) 2006-07-20 2015-11-03 G. Lawrence Thatcher Bioabsorbable polymeric composition for a medical device
US8329621B2 (en) 2006-07-25 2012-12-11 Halliburton Energy Services, Inc. Degradable particulates and associated methods
US7687438B2 (en) 2006-09-20 2010-03-30 Halliburton Energy Services, Inc. Drill-in fluids and associated methods
US7678742B2 (en) 2006-09-20 2010-03-16 Halliburton Energy Services, Inc. Drill-in fluids and associated methods
US7678743B2 (en) 2006-09-20 2010-03-16 Halliburton Energy Services, Inc. Drill-in fluids and associated methods
US20080102272A1 (en) * 2006-09-21 2008-05-01 Yuichiro Sakamoto Adhesive wrapping film
US20080076695A1 (en) * 2006-09-26 2008-03-27 David Uitenbroek Dryer sheet and methods for manufacturing and using a dryer sheet
US20080076313A1 (en) * 2006-09-26 2008-03-27 David Uitenbroek Wipe and methods for manufacturing and using a wipe
US7947644B2 (en) 2006-09-26 2011-05-24 Wausau Paper Mills, Llc Dryer sheet and methods for manufacturing and using a dryer sheet
US20080076314A1 (en) * 2006-09-26 2008-03-27 John James Blanz Wipe and methods for manufacturing and using a wipe
US9724864B2 (en) 2006-10-20 2017-08-08 Orbusneich Medical, Inc. Bioabsorbable polymeric composition and medical device
US9211205B2 (en) 2006-10-20 2015-12-15 Orbusneich Medical, Inc. Bioabsorbable medical device with coating
US7686080B2 (en) 2006-11-09 2010-03-30 Halliburton Energy Services, Inc. Acid-generating fluid loss control additives and associated methods
US8220548B2 (en) 2007-01-12 2012-07-17 Halliburton Energy Services Inc. Surfactant wash treatment fluids and associated methods
US20080268018A1 (en) * 2007-04-30 2008-10-30 Pacetti Stephen D Method for forming crystallized therapeutic agents on a medical device
US8006760B2 (en) 2008-04-10 2011-08-30 Halliburton Energy Services, Inc. Clean fluid systems for partial monolayer fracturing
US7906464B2 (en) 2008-05-13 2011-03-15 Halliburton Energy Services, Inc. Compositions and methods for the removal of oil-based filtercakes
US8916080B2 (en) * 2008-06-13 2014-12-23 Toray Plastics (America), Inc. Method to produce matte and opaque biaxially oriented polylactic acid film
US20120128973A1 (en) * 2008-06-13 2012-05-24 Toray Plastics (America), Inc. Method to produce matte and opaque biaxially oriented polylactic acid film
US20090311544A1 (en) * 2008-06-13 2009-12-17 Toray Plastics (America), Inc. Method to produce matte and opaque biaxially oriented polylactic acid film
US8911870B2 (en) * 2008-06-13 2014-12-16 Toray Plastics (America), Inc. Method to produce matte and opaque biaxially oriented polylactic acid film
US7960314B2 (en) 2008-09-26 2011-06-14 Halliburton Energy Services Inc. Microemulsifiers and methods of making and using same
US7833943B2 (en) 2008-09-26 2010-11-16 Halliburton Energy Services Inc. Microemulsifiers and methods of making and using same
US20100126685A1 (en) * 2008-11-25 2010-05-27 Dixie Consumer Products Llc Paper Products
US8016980B2 (en) 2008-11-25 2011-09-13 Dixie Consumer Products Llc Paper products
US7998910B2 (en) 2009-02-24 2011-08-16 Halliburton Energy Services, Inc. Treatment fluids comprising relative permeability modifiers and methods of use
WO2010105142A1 (en) 2009-03-13 2010-09-16 Natureworks Llc Recovery of lactic acid values from a meso-lactide stream
WO2010105143A2 (en) 2009-03-13 2010-09-16 Natureworks Llc Methods for producing lactide with recycle of meso-lactide
US8552209B2 (en) 2009-03-13 2013-10-08 Natureworks Llc Recovery of lactic acid values from a meso-lactide stream
US8674056B2 (en) 2009-03-13 2014-03-18 Natureworks Llc Methods for producing lactide with recycle of meso-lactide
US9035076B2 (en) 2009-03-13 2015-05-19 Natureworks Llc Recovery of lactic acid values from a meso-lactide stream
US8082992B2 (en) 2009-07-13 2011-12-27 Halliburton Energy Services, Inc. Methods of fluid-controlled geometry stimulation
US20120220697A2 (en) * 2010-03-16 2012-08-30 Andersen Corporation Sustainable compositions, related methods, and members formed therefrom
US20110230599A1 (en) * 2010-03-16 2011-09-22 Michael James Deaner Sustainable Compositions, Related Methods, and Members Formed Therefrom
US11667981B2 (en) 2011-04-07 2023-06-06 Virdia, Llc Lignocellulosic conversion processes and products
US10876178B2 (en) 2011-04-07 2020-12-29 Virdia, Inc. Lignocellulosic conversion processes and products
US8829097B2 (en) 2012-02-17 2014-09-09 Andersen Corporation PLA-containing material
US9512303B2 (en) 2012-02-17 2016-12-06 Andersen Corporation PLA-containing material
EP2862890A1 (en) 2012-05-03 2015-04-22 Virdia Ltd. Method for the extraction of lignin from biomass
US11053558B2 (en) 2012-05-03 2021-07-06 Virdia, Llc Methods for treating lignocellulosic materials
EP2878614A1 (en) 2012-05-03 2015-06-03 Virdia Ltd. Methods for treating lignocellulosic materials
US9783861B2 (en) 2012-05-03 2017-10-10 Virdia, Inc. Methods for treating lignocellulosic materials
US9493851B2 (en) 2012-05-03 2016-11-15 Virdia, Inc. Methods for treating lignocellulosic materials
EP2878349A2 (en) 2012-05-03 2015-06-03 Virdia Ltd. Fractionation of a mixture by sequential simulated moving bed chromatography
WO2013166469A2 (en) 2012-05-03 2013-11-07 Virdia Ltd Methods for treating lignocellulosic materials
US9631246B2 (en) 2012-05-03 2017-04-25 Virdia, Inc. Methods for treating lignocellulosic materials
US9650687B2 (en) 2012-05-03 2017-05-16 Virdia, Inc. Methods for treating lignocellulosic materials
US9708761B2 (en) 2013-03-08 2017-07-18 Xyleco, Inc. Array for processing materials
US10549241B2 (en) 2013-03-08 2020-02-04 Xyleco, Inc. Enclosures for treating materials
US9464334B2 (en) 2013-03-08 2016-10-11 Xyleco, Inc. Array for processing materials
US9334518B2 (en) 2013-03-08 2016-05-10 Xyleco, Inc. Array for processing materials
US9816231B2 (en) 2013-03-08 2017-11-14 Xyleco, Inc. Processing materials
US10066339B2 (en) 2013-03-08 2018-09-04 Xyleco, Inc. Processing materials
US10105652B2 (en) 2013-03-08 2018-10-23 Xyleco, Inc. Array for processing materials
US9371550B2 (en) 2013-03-08 2016-06-21 Xyleco, Inc. Processing materials
US10294612B2 (en) 2013-03-08 2019-05-21 Xyleco, Inc. Controlling process gases
US10518220B2 (en) 2013-03-08 2019-12-31 Xyleco, Inc. Processing materials
US10543460B2 (en) 2013-03-08 2020-01-28 Xyleco, Inc. Upgrading process streams
US9611516B2 (en) 2013-03-08 2017-04-04 Xyleco, Inc. Controlling process gases
US9388442B2 (en) 2013-03-08 2016-07-12 Xyleco, Inc. Reconfigureable processing enclosures
US10610848B2 (en) 2013-03-08 2020-04-07 Xyleco, Inc. Processing materials
US10682623B2 (en) 2013-03-08 2020-06-16 Xyleco, Inc. Array for processing materials
US10577494B2 (en) * 2014-12-22 2020-03-03 3M Innovative Properties Company Compositions and films comprising polylactic acid polymer, polyvinyl acetate polymer and plasticizer
US11254812B2 (en) * 2014-12-22 2022-02-22 3M Innovative Properties Company Compositions and films comprising polylactic acid polymer, polyvinyl acetate polymer and plasticizer
US20170313912A1 (en) * 2014-12-22 2017-11-02 3M Innovative Properties Company Compositions and films comprising polylactic acid polymer, polyvinyl acetate polymer and plasticizer
US11787929B2 (en) 2014-12-22 2023-10-17 3M Innovative Properties Company Compositions and films comprising polylactic acid polymer, polyvinyl acetate polymer and plasticizer
US11066551B2 (en) 2016-05-20 2021-07-20 3M Innovative Properties Company Oriented polylactic acid polymer based film
US10982090B2 (en) 2016-06-21 2021-04-20 3M Innovative Properties Company Graphic articles comprising polylactic acid polymer based film
EP3406605A1 (en) 2017-05-22 2018-11-28 NatureWorks LLC Methods for producing lactide with recrystallization and recycle of meso-lactide

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